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Oil
Understanding how oil lubricates, an in depth discussion.
LUBRICATION THEORY.
What you should consider in selecting oils, etc.
https://bmwmotorcycletech.info/oilessay.htm
51C
© Copyright 2024, R. Fleischer
The importance of proper engine oil in an Airhead motorcycle:
Most any engine oil will work reasonably (but not necessarily best, or near best) for the engine, but there are specific areas of the engine that WILL BE (or can be) damaged, and perhaps expensively, if the oil is not of proper quality and that means proper base stock and proper additives are included by the oil makers. Certain specific ingredients in engine oil are very much needed to avoid $$$ problems in your BMW Airhead motorcycle. Three are potentially critical. One of them is ZDDP (or ZDP, ZDTP). The amounts in common car type oils have been decreased, over time, in accordance with API, SAE, and oil and auto manufacturer's changes. Your Airhead motorcycle requires one of the types of these substances in a minimum (and maximum) amount, to avoid spalling and other deterioration of the camshaft and cam follower surfaces. There are no fully adequate substitutes, in regards to your Airhead motor requirement. Another ingredient is needed to be sure that under storage conditions, the cam and followers (and other items in the engine) do not have the oil dripping off and leaving the metal unprotected at engine startup. The final ingredient (of major importance) is that the amount of detergents (increasingly higher in modern car oils) should NOT be excessive, as that defeats both long term storage metal protection & defeats the protection of ZDDP type products.
PRELIMINARY & BASICS:
There are several lubrication articles on this website. They are generally in the section of articles 49 through 51D. Have you read them all?
Additives are put into refined base stock oils to help form better 'thin oil films', so the oil is not pounded-out by impact forces. The oil can also be 'moved out' by rotating forces that make the oil create something like ocean waves. Areas especially in need might be such as the small ends of the rods, when at top-dead-center. Very little engine wear is from dynamic friction ...that is, from rotating, or constantly shearing movements. Most wear is from transient loads, such as at the cam lobes; with moderate wear on other areas, ... especially during cold startup. Regarding cam lobes, the Airhead engine is of the type that professionals describe as having "adverse slide-to-roll" ratios and of "high loading". These types of engines are common to those of "flat-type" cam/rocker/follower systems, such as on the old VW Beetle, the Porsche 356, early Corvette's, even the Ford Pinto. Owners of these types of vehicles are not happy about engine failures from wrong types of oils. In particular camshaft and lifter wear. Modern car engines are so precisely designed and manufactured, that very light oils with no or limited ZDDP additives can be used. That is why modern car oils have so little ZDDP type additives (and, some others)...and, of course, you know that what additives must be used must not interfere with expensive catalytic converters. Not so with many earlier engines. The BMW Airheads are medium-old technology. The BMW Classic K bikes (K1, K75, K100, K1100, and K1200) are somewhat more modern, with exceptions to the very first of the K100, which are a bit more into the medium-old group of engines for some nerdy reasons.
Much has been said about synthetic oils, and mostly it is about how much better they are than petroleum oils. While based on quite a few facts, especially misleading is that oil change intervals may be increased greatly. While relatively true (doubling, or a bit more perhaps, in some situations) for the lubricating qualities, it is not necessarily true as far as the additives for swelling the seals (without which the seals would shrink and leak); and it is even more not necessarily true for the ability of the particular oil to deal with acids...etc... that accumulate in the oil, etc. One can make a pretty good argument that the anti-wear additives are considerably depleted after enough mileage. BUT, it is not just mileage, but type of usage, and frequent cold starts, high humidity, very short trips, etc. These are very hard on the oil.
Fuels contain sulfurs which react with moisture from combustion, condensation, etc., to form acids. Petroleum oils, as opposed to most full synthetic oils, also contain sulfurs. Very short trips, particularly in cold weather, let moisture accumulate in the oil. Lots of cold weather starts and low mileage per start, all lead to oil contamination and degradation. Some synthetic oils are compounded with longer-lasting additives and amounts to deal with contamination, & oil change intervals can be safely extended, depending on your riding habits, whether you do many very short trips (less than 40 or so miles), etc.
You may have heard that it takes 10 miles or more to heat up the oil enough to 'burn-off' accumulated moisture (moisture in the oil is very damaging over the long term). The wording of those statements should be: "begins to burn-off". Under about 8 miles or so, little moisture is burned-off, and it takes about 20 to be meaningful ....and it can take a lot more, in many circumstances.
Most very modern seals are neoprene or silicone types, usually not needing specialized swelling agents in the oil. Keep in mind that your Airhead, or even Classic K bike, might have early seals in it that are not all that compatible with many a full synthetic oil; and, some seals are not modern types even as sold today.
For Airheads, one of the important protective additives is some form of ZDDP or ZDTP. These are for flat tappet (flat cam follower) type of operation, in enough ...but not excessive ...concentration. The early classic K bikes, ~1983-1986 K100 type bikes, also need this protection. Few seem to know about THAT.
There are a lot of additives in oils. Some protect against absorbed moisture and many other potential problems. Some additives 'burn off' rather too easily, leaving the oil without enough of the additive. Some oils have way too little, even none of the additives that Airhead engines require. Some few pricier oils, made/sold for motorcycles, have considerably more of the additives, so that as the oil has more and more miles or stop and go miles on it, enough of the additives are left to do a decent job. There are limits to time/miles/startups, etc....and there are limits to the amount of the additives that can be added, before excessive additives begin to cause problems. Additives are used for many functions. Just how often to change oils, based on time and mileage, depends considerably on how the engine is operated, the type of oil, etc.
Use of premium & super-premium oils can be warranted, depending on many things, including how long you will own the vehicle, over how many miles. In the over-all expense of operating a vehicle, oil is usually a low/moderate cost item; thus, use of a better oil, that protects better, is something that usually will pay off ....particularly if the owner intends to keep the vehicle a long time. If you sell a vehicle with careful maintenance records, it is entirely possible that showing you used a premium engine oil may well pay off for doing so.
There are many tests done on oils that are not generally talked about, except between lubrication engineers. While I mention, in this long oil essay article, how some oils 'burn off' some of their oil rather quickly, I don't get into it deeply. But, it can affect your wallet ....compared to oils that don't seem to hardly burn much ....all in the same engine, same circumstances of use, etc. One of these specialized tests is called the NOACK. That test is supposed to simulate what happens at the extreme temperatures oils are exposed to in all engines at very specific places in those engines. When engine oil temperatures are commonly talked about, it means the oil temperature in oil tanks in dry sump engines, or in oil pans such as on your Airhead. But, oil that is circulating in the cylinder head is exposed to vastly higher temperatures around the valve guide, and other areas of the valve. This is particularly so at the exhaust valve area, but also somewhat in the upper cylinder area where small amounts of oil are exposed to extreme oil temperatures. The cylinder walls are lubricated, in extremely thin oil layer amounts ....often just a fraction of a drop perhaps, over the whole cylinder. That oil comes in contact with the very hot top piston ring(s). The NOACK test is done at 250°C (yes, Centigrade). That is 482°F. All engine lubricating oils will 'evaporate' or are 'burned', or otherwise changed, by such temperatures. Unless your engine is using a very small amount of oil per oil change period, your actual oil cost might be considerably higher with oils that 'burn off' quickly ...very noticeable if you have-to add much oil between changes. Rather often, the initial half quart or so of oil 'disappears' rather quickly. That is often due to breather system condensing or putting into the atmosphere, a drop of oil here and there, which over time, adds up. Believe it or not, you can lose a quart of oil if losing a drop per mile. These things are just one example of 'engineers oil talk'.
The rest of this article delves quite deeply into lubricating oils for vehicles, how they actually do their job, recommendations, hints, etc.
Special notes, regarding modern CAR oils IN CARS! ...and comparison with Airheads:
Things have changed since very approximately 1990, radically so in some instances, in what type of lubricating oil is needed for modern cars. I am not speaking here of certain things in the following article about ZDDP and ZDTP that are needed in some old flat tappet cars, & in the Airheads, & in the earliest K 100 models, etc. I speaking of MODERN cars ...and ...I am deviating for just a moment here to offer you some cautions, as failure to understand and keep these things in mind can cost you $$$$. There are several situations that have become big expensive problems for MODERN car owners.
1. The use of small extremely high speed turbochargers is becoming very common, even on less expensive cars, as small engines with turbochargers can have improved fuel mileage while helping to maintain horsepower. The first generation of these, which required special oil, is long gone now, but even newer designs require special oils. Some designs have, or had, oil reservoirs to protect the turbocharger bearings during engine turn-OFF (as the turbocharger slows down), others do/did not. This means that more frequent oil changes and using ONLY approved oils (approved specifically by brand and model of oil by the car manufacturer) are really a NECESSITY.
2. Oil compounding is generally critical with engines with controlled camshaft timing.
3. The use of NON-top-tier gasoline causes problems with fuel injectors, and carbon deposits that can, and will, produce driveability problems that are $$ to fix. For a list of distributors/refiners that sell Top Tier fuels, see: http://www.toptiergas.com/ Click around at the headings at the top.
4. More and more gasoline engines for cars and trucks are being manufactured with DIRECT cylinder fuel injection. This usually means the use of very high pressure pumps, often driven from one or more lobes of the valves camshaft. The gasoline makeup and type of oil is MUCH more critical for deposits that affect driveability (surging, bucking, lousy start-up, poor cold running, lousy mileage ...and more). It is DIFFICULT on many of these engines to clean-up any deposits. Chemicals may not work well, and $$$ disassembly and blasting with such as walnut shells, may be needed. Removing and replacing a cylinder head (or two) for this is NOT CHEAP.
The bottom line for MODERN CARS, as a general rule, is:
Use ONLY the brand, model, and grade, of engine oil and engine oil filter, that the car manufacturer has recommended. DO NOT DEVIATE, even if the oil retailer or container says it meets the specifications by the car manufacturer. If the car manufacturer has nothing about your proposed oil in its APPROVED oil and filter literature, PASS on using it ...or, study-up some, and then decide.
Modern oils for cars are usually classified as 'energy saving', which has connotations FAR beyond those words! Use of high dosage additives (30% is not unusual) and thin oils (5W30 or 0W30, etc.) is common. There is even a 0W16 oil becoming popular...and specified by manufacturer's. Very strict attention to engine design/manufacture is necessary to support the use of such oils. Modern engine design and construction is so good that it is now considered 'normal and expected' for engines to not require valve jobs or piston rings, etc., for 1/4 million miles. Burned oil smoke coming out of the exhaust is mostly a memory from the pre-eighties.
This is "relatively true" for the Classic BMW K bikes. It is vastly less true for the Airheads. If Airheads had all been water-cooled, and with precision Nikasil cylinders, they, too, could have top ends that lasted vastly longer. As it is, Airheads need a top end job by 60,000 to 120,000 miles. The earliest Airheads, before the Nikasil cylinders, would usually be on the lower area of those figures. But, enough on this, because I could write more paragraphs, and bore you even more.
ZDDP (and ZDTP):
NOTE that these two additives are NOT in all engine oils, and when they are, the concentrations vary considerably!
ZDDP (zinc dialkyl-dithiophosphate) is a common anti-wear additive for use in mineral-based oils.
ZDTP is approximately the equivalent (zinc di-thiophosphate), which is used in synthetic oils.
Both are usually just said in common usage to be ZDDP. Both have been used as an anti-wear ingredient in engine oil for many decades. ZDDP and ZDTP are some of the many additives that are put into conventional motor oil to improve lubrication and longevity qualities.
IN THE ARTICLE THAT FOLLOWS, USE OF "ZDDP" CAN MEAN EITHER ZDDP OR ZDTP (AND THERE IS ANOTHER VERSION TOO), OR BOTH, OR ALL.
Many premium motorcycle oils are produced with large percentages of synthetic components, and may well have quality additives that will last longer than the commonly accepted (and most often WRONG!) 3,000 mile change intervals. It depends CONSIDERABLY on the 'quality' and amount of additives, and particularly how the motorcycle is ridden ...such as very short 3 mile trips in high humidity or cold weather perhaps ...versus over 20 mile average trips. Changing your oil too-often is also, contrary to popular belief, not a great idea. I know that sounds wrong ...and the reasons are complex, so I won't get into them here. If you do not believe, me, do some of your own research! I will cite one SAE study, later in this long article, to save you that trouble.
There is a problem with the word synthetic. Due to a lawsuit won by Castrol (versus Mobil), a judge made a ruling that a highly refined petroleum oil, not a complete full-synthetic oil, can, if the manufacturer wished, be called synthetic. Because of this ruling, so-called part, or even full-synthetic oils may not truly be the highest quality real synthetic oils. Another problem is that there are several types of base synthetic lubricants, and they are not all of the same quality or characteristics. I will get into them later in this article. I personally have no problem with the synthetic or not really synthetic argument, if the resulting oil for your engine was equivalent in performance; unfortunately, they are not usually very close.
Bluntly speaking, Castrol ...and some other companies ...know quite well that the Public is not knowledgeable about oils, and these companies know that the public is typically enamored with buzz-words, such as Synthetic, Laser, etc. Yes, those words have produced 'outer space' sort-of emotions, which sells product. These companies also know that the vast majority of products are purchased by price, not quality. Many companies have made quite a lot of money, for decades, by selling worthless products for vehicles, like certain additives you put in the fuel tank or engine. I am not saying all Castrol products are like this, not at all. What I do want you to understand is that there is a lot of misleading advertising, part-truths, insufficient information, etc. I suggest you be somewhat cynical about what you purchase. Maybe, just maybe, you will read this article, and some of my other articles, and get the idea that I view myself, and hope you do too, as an educator, trying to help those who do their own work, or be knowledgeable about what is done to their vehicles by others. I especially would like this, regarding our wonderful antique Airheads.
Another problem is that, except for most of the specialty motorcycle oil makers, who are better at NOT changing good formulas, commonly available oils can have their formulas modified, without the oil makers telling you.
For most practical purposes, IF your oil, synthetic as named.. or not, ...contains a reasonable amount of ZDDP or ZDTP, it is likely going to be OK and you can go further than you may think before needing an oil change for your Airhead. Some oils will 'burn off' faster at the beginning, and that costs-you; but you will probably overlook that. BTW, that early burn-off really is usually NOT anything much more than 'blowby' or from crankcase turbulence from thrashing rotating parts. What usually happens is that the higher oil level and increased crankcase turbulence, causes more oil vapor to get into the engine oil breather system, and be exhausted to the atmosphere. BMW knew this, and one of my article describes, and shows an engine cutaway, that is of the teensy oil hole BMW added, later in Airhead production, to allow much of the blowby oil to condense and be returned to the crankcase.
What you should look out for is that the oil is OK for your particular motorcycle. Oil is considerably more critical for Airheads, as far as scuffing and lubrication goes. For the Classic K bikes, use of the proper oil, a quality full synthetic, is very likely to greatly extend the life of the starter motor sprag clutch, which is buried deep inside the engine area, and is very costly to replace, the labor alone is VERY expensive!
Diesel and/or 'fleet' oils like Rotella-T and Delo and Delvac are all likely to have SOMEWHAT reduced amounts of ZDDP in them NOW ...and perhaps even less as time goes on. Delo 400 is OK for a gasoline engine. Rotella-T should be more than just OK, and seems to be well-formulated...but do not use the new T1 Rotella, the ZDDP is much too low. These oils are not 'only for diesels'. If curious enough, get the manufacturer's literature and read the fine print, and notice the characters (letters and numbers) that describe the approved service for the oil. While air-cooled motorcycle engines are much harder on oils than water cooled engines, these 'fleet' oils may well do just fine for you. You may save some money.
Your Airhead NEEDS ZDDP or ZDTP; but does not need the very high dispersant and some other qualities of some diesel oils that might give problems, especially in the past, on CD diesel oils. I do not recommend all modern diesel oils for Airheads. You might carefully select one, but I am not fully endorsing any of them. I do think that probably Rotella and Rotella-T, and Delo, are OK, particularly the original Rotella-T. Modern car oils have little (some none) ZDDP, as the zinc component of ZDDP tends to poison catalytic converters. The substitutes in modern car oils are not adequate for Airheads. Levels of zinc of 800 ppm (parts per million) and below are not adequate for Airheads. Levels between 1300 ppm and 1800 ppm are preferred for Airheads.
Modern car oils are typically "energy saving" (and so marketed and marked with a symbol on the container), are usually in thin grades such as 0W30 and 5W30, ...and NO true Energy Saving oil, of ANY viscosity, is fully compatible with your Airhead, and not good for your classic K bike either.
There is a lot of confusion over SAE graded oils, and ZDDP. Simply-put, if a viscosity grade of oil is deemed by the SAE, API, and vehicle industry, to NOT be a car/truck viscosity grade, then the oil manufacturer "may" put such as a goodly dose of ZDDP and other stuff into the oil. Doesn't mean they have done so. 20W50 is such a grade. Thus, a premium motorcycle oil maker MAY put lots of ZDDP...and other good stuff.... into a 20W50. He may do it in 10W40, 15W50, etc. ...as these are also not considered car oils.
More information: https://bmwmotorcycletech.info/viscosity.htm see particularly near the end, where I list ZDDP levels.
Also see: https://bmwmotorcycletech.info/oilcansimple.htm
From this point onwards in this article things will generally be more technical.
Thick oils, that is, oils with higher viscosities, have more internal friction, but CAN support larger loads ....but! ...there's always a but!, EH? ....HIGH mechanical pressures of/in the parts themselves INcrease oil viscosity. This is another of those common sense things that makes you THINK that it is "WRONG" ...but ....yes, it is true. When oil is inside a common bearing, and the bearing has lots of pressure (think conrods, as one example), the oil's effective thickness INcreases. This is so even with the ends of the bearing open to 'release trapped oil'. This is a special property of "thin oil films", and has very little to do with mechanical pressure in and of itself as a trapped medium. Yes, I know this all sounds quite wrong.
A THIN (lower viscosity number) oil is vastly easier to pump and thereby get through the lubrication system, and into vital areas quickly, and will support massively heavy loads. So, a manufacturer may well use tighter tolerances on those bearings, less clearance and a thinner oil. This engine then needs more oil pump pressure, but that increases fluid friction. No entirely free lunch here. Another factor is high rotational speeds. The faster the surface speed, the more the oil is formed into a cushion, which allows even higher loading. There are many types of surfaces in our motorcycles. Some slide, some roll, some are fluid-based. There are a lot of forces and peculiar things at work.
Oil and oiling/lubrication is hardly just some sort of liquid slippery stuff.
What folks sometimes want to know is how lubrication really deals with friction. You can't eliminate friction on a practical basis; but, you can minimize it. Many decades ago, schooling about friction was a sort of 'hills & valleys' type of discussion in describing forces that resist sliding motion. In other words, parts that looked smooth, really had microscopic hills and valleys and it was those that caused the friction of the parts. That concept is rather obsolete now. It still applies, of course, to such as breaking-in of new piston rings, and most other areas ... to some extent. Today, with modern fine-machining, stable alloys, and so on, the more important concept is adhesion; and, lubrication engineers may sometimes find extreme problems that they need to solve: cold-welding of surfaces in contact, as one example.
When a full film of lubricant separates surfaces, the only friction is from motion within the fluid. When you stop to think about this, it DOES, YES, sound crazy! Common Sense is wrong, for the 3rd time in this article you are reading.
Here is what really happens:
The fluid (oil) splits into layers. The top layer sticks to the surface, bottom layer sticks to the lower surface, and each successive layer travels at a lower speed, which shears the layers on either side. Oil "film" is what does the lubricating (not absolutely true on a REAL engineering basis, but good enough for us, here). There are several types of 'oil films'. The hydrodynamic film is only perhaps 0.001" thick in a 1 inch bearing. Surfaces are kept apart by several functions, one of which is the hydrostatic function which is primarily from oil pressure from the oil pump. Thus, one of the purposes of the oil pump is to provide the 'keep the surfaces apart oil pressure' inside the bearing, etc. This is critical when there are slow heavy loads and thusly for the starting up of the engine. Please be sure to read this small paragraph again ...oil slipperiness is not really involved! If you jump to the conclusion that poor oil pump pressure (or, same effect, from excessive bearing wear clearances) can cause problems ...you would be correct.
If the oil film gets too thin, metal contact is possible. Typically this won't happen until the film is ten times less thick than that 0.001" mentioned. At that point, you want additives like ZDDP, etc. Some additives found in larger amounts, in diesel oils in particular, can cause problems in HIGH SPEED engines. Thus, one of the reasons I am hesitant to fully approve diesel oils in high rpm gasoline engines, are those problems. Some of the old CD-x diesel oils were like that. NOTE that diesels are used in many cars, particularly common in Europe, and some of these engines are relatively high rpm types. Thus, the specifications for diesel engine lubricating oils have changed over the years. The Europeans were much better at this than the Americans.
From what you have read so far, you understand that you do not want too thick an oil, nor do you want too thin an oil. There are also reasons for not too low, nor too high, oil pressure. There IS A REASON that 5W30 or 10W30 ...and possibly 10W40 ...are all too thin (and have other not great characteristics) ....for most Airheads and K bikes riding in mild temperatures. There ARE REASONS that 15W50 or 20W50 oil is most often recommended. This also applies to K-bike engines. There are oils with a wider range, like 10W50. While much less true today; decades ago, multi-grade oils in the widest viscosity ranges were not very good, not much better than straight grades, at least after some miles. Today, straight weight oils have little use in engines; however, the widest range oils, such as 10W50 from some manufacturers, are still not as good as narrower range oils. 10W50 oil is just about never as good for your Airhead, as 20W50.
As parts speed up, other factors come into play. Required or specified oil viscosity can be juggled somewhat by the engine manufacturer. Increasing viscosity will allow more loading, but then you get friction-caused higher temperatures; and also less immediate oiling. Speed of the parts means faster shearing of all layers, but speed helps form a cushion, so higher speed means higher allowed loading (read that again, and think about what you have heard about 'lugging' an engine). The best approach for a manufacturer is usually to use a reasonably low viscosity oil, with very good thinning characteristics (high viscosity index) so the oil does not thin too much with temperature rise.
When the K bikes came out, BMW contracted with Spectro Oils to produce an oil specifically for the water-cooled K bikes. BMW then promoted that oil (a bit slyly when they did that for Airheads, it wasn't the very best for them, although 'adequate'). The oil that Spectro made for BMW was not Golden Spectro, and was not standard Spectro either. Golden Spectro was a better oil, than BMW oil, IMO. There were problems with early K bikes starter sprag clutches with petroleum oils, that were mostly cured with the use of full synthetic oils. BMW modified the design more than once. In the very beginning of the K-bike production, BMW was having problems with the K bike starter sprag drive clutch not engaging, and BMW redesigned it by adding more sprags and more holes for better oil flow. The updated assembly gave far fewer problems, but some problems still showed up now and then. BMW offered a full synthetic oil later on. Mobil 1 works quite well, with very few problems with any of BMW's starter sprag clutches. What happened when the starter sprag clutch began to fail is that it would slip after some sort of unseen glazing film or sprag shape wear accumulated; and, perhaps, some loss of sprag clutch springs tension; ...and synthetic oils helped a lot (particularly with deposits buildup in the sprag clutch internals) ....as did some synthetic additives in the Spectro synthetic oil as well as the original Spectro from BMW. The Mobil 1 brand has 15W50 and 20W50 oils specifically for motorcycles; although Mobil does change, irregularly, on the exact formulation of what is being sold. They do have an oil that was designed for Harley Davidson's, the V-Twin oil.....there have been various names for that oil over the years. It has a quite goodly amount of ZDDP in it, and seems to be very good in Airheads. I prefer the 15W50 Mobil 1 for the K1, K75, K100, K1100, K1200. However, some have used that oil for the Airheads. I haven't made up my mind on it, mostly because the ZDDP is lower than I'd like to see it. BTW ...Harley Davidson has gone to full synthetic oils ...for heat reasons, I think.
Rislone, and a few other additives, perhaps the stronger CD2 ...used once if needed ...for a hundred or so miles ...will sometimes fix the K bike starter sprag clutch, which has a very high labor charge job to replace; and the part is not cheap either. It is actually possible to remove a failed later type starter sprag clutch and clean it (PROPERLY!!!) and have it work again ...but few do that, due to the intensive labor, if the cleaning does not work well.
BMW is hardly the only company having starter motor clutch problems. The common Honda Gold Wing used what amounts to fat rollers or roller bearings if you wish, to provide a one-way clutch, and they have a habit of gumming up from oil residue varnishes, etc. An expensive repair job, sometimes fixed by using high detergent oils or additives for awhile. BMW K bike starter sprag clutch problems results in a high cost repair job, as noted, and the same high detergent additive routine may work. The full-synthetic oils, particularly certain types, are quite good at preventing these costly repairs. It is too bad that the old starter clutch methods, of a Bendix assembly, were not designed-into the K bikes.
Classification of types of lubricating base oils:
This particular section was plagiarized from several combined internet articles, and then highly edited by me, and there is a large amount of my own material here. Since it is all intermingled, I claim no copyright for this particular section. Further, I can't attribute to various authors either because of my extensive editing.
The American Petroleum Institute (API) classifies base oils under five categories of Groups. These categories help identify base stocks in finished oil formulations to help ensure that engine oil performance demands are met.
Group I:
Conventional mineral oils derived from refining selected crude oil fractions. Solvent processing, first used in the 1930s to improve base oil performance, is still used today to produce Group I lubricant stock. While some automotive oils on the market use Group I stocks, they are generally used in less demanding applications. These are the old high paraffin (wax) base oils. They are not used for modern engine oils anymore but can still be found in those little bottles or small cans with pull spouts on all-purpose household oil you buy at the hardware store for stuff like oiling door hinges.
Group II:
With the development of "hydrotreating"; and "hydrocracking" technology, refiners introduced more highly refined, low wax base stocks, or oils. While refined to a greater extent than conventional mineral base oils, these hydro-processed base oils still have performance limitations due to the presence of undesirable impurities. Group II base oils are common in mineral based motor oils currently available on the market and have fair to good performance in lubricating properties. This is the standard petroleum base stock that all modem conventional petroleum oils are made from. Quality varies widely depending on where it was "dug up from". Even in "finished" form it can contain various amounts of paraffin (wax), impurities left over from refining and from the ground it came from. Chemically it is a hodge podge of different sized hydrocarbon molecules, not all of which "get along with each other" ...so to speak. The result of this is a product that produces sludge, varnish and mechanical wear as it ages and breaks down in service. That does NOT mean that this is not a good usable oil for many purposes. These oils have steadily been improved over the years as API (American Petroleum Institute) services requirements have gotten stricter. However as modern engines pump more horsepower from smaller engines with less total oil sump capacity and the level of horsepower/torque transmitted though today's light weight fuel efficient drive trains continues to climb, lubricant manufacturers find that conventional petroleum oils really just cannot be improved much farther. Hence the move we see by automakers to synthetic fluids; both in engines and transmissions & differentials. Combine that with the need to improve fuel economy (and synthetic lubricants have the ability to do that) and you can see why "factory filled with synthetic" is becoming more and more common in cars and some bikes. I am not
going to dig deeper into this Group Two, that is, into arguments about super-modified petroleum oils that are or are not to be considered synthetics. Castrol won that argument in court, as you saw from reading much earlier and will again, below, in this article.
Group III:
Group III base oils are also manufactured using the hydro-treatment process but are subjected to higher temperatures or processing times. These highly hydro-processed, or "non-conventional" oils, have greatly improved oxidation stability and low temperature performance, but still contain some undesirable impurities that cannot be easily removed, so they are not removed. These high quality Group III base oils are now widely available in North America because they can be manufactured by most companies making Group II oils.
Group three oils are petroleum oils that have been hydroisomerized, "hydro-cracked" as it is commonly called. This is the most stringent level of petroleum oil refining. Much of the paraffin and impurities have been removed and its performance on any number of industry tests is substantially better than Group Two. Although not made from truly synthesized engineered molecules and as such not a true synthetic oil (as far as I am concerned!, see just below paragraph), it does offer a goodly portion of the benefits you would expect from a true synthetic and in fact is usually sold and marketed as a 100% synthetic product.
The vast majority of synthetic oils on the market are actually made from group three oils because of a "lawsuit" some years ago between Mobil and Castrol, that totally changed the synthetic oil industry. Because of this lawsuit the buying public has largely been duped into believing that these oils are actually a real synthetic. Mobil Inc., makers of Mobil One (Mobil 1), sued Castrol Inc., makers of Castrol Syntec, accusing them of marketing a hydro-cracked petroleum oil as a synthetic. Mobil's primary argument was that Castrol Inc. had pursued an unfair market advantage because Group Three based oils are much less expensive to manufacture than true synthetic oils, yet Castrol was marketing Syntec as a 100% synthetic product. Castrol could make it for less, sell it for less, and un-fairly under-cut all it's competitors prices in the synthetic oil market with a oil that was not truly a synthetic product.
In the end though, Castrol convinced the judge that a Group Three based oil has been sufficiently refined that it should be able to be marketed along with true synthetic oils. Basically the court expanded the definition of synthetic to include group three based oils. Because the synthetic oil market is the fastest growing part of the lubricants industry, manufacturers are eager to jump up and grab the profits for the sexy-customer-grabbing-word "synthetic" on the bottle. Car makers are starting to specify synthetic oils, particularly on turbocharged engines. Group three oils do not have the performance of true custom-engineered synthetic oils, especially in temperature extremes. The vast majority of what is being sold as synthetic are really Group Three petroleum-based oils. The public for the most part doesn't know the difference.
Group IV:
API has classified synthetic engine oils made with PAOs as a special class of base stock. The term "synthetic" was originally used to refer to Group IV (PAOs) and V (see below) base stocks. With the growth of the PAO market, some base oil manufacturers began manufacturing Group III mineral oils that provide equivalent performance to PAOs, and marketing these as "synthetic" oils. In 1999, a ruling by the National Advertising Division of the Council of Better Business Bureaus broadened the definition of "synthetic lubricants" to include high-performing products made with Group III base stocks. Polyalphaolefin and related olefin oligomers and olefin polymers synthetic hydrocarbon or PAO's as they are commonly called, are a true man-made-engineered base oil produced by catalytic reaction with various alpha olefin compounds. PAO's are widely recognized as providing outstanding performance for many lubricant applications because of very high viscosity index, a wide operational temperature range and because they are thermal and shear stable. PAO's also have low promotion of corrosion and are compatible with mineral oils and the range of materials that engines and other machinery are manufactured from. The molecular structure of PAO's are easily customized for use in all kinds of applications from automotive to industrial and are widely used in motor oils, gear lubes, high temperature/extreme pressure greases, compressor oils and hydraulic fluids.
Group V:
These specialized base oils, with few exceptions, are chemically engineered stocks that do not fall into any of the categories previously mentioned. Typical examples of Group V stocks are esters, polyglycols and silicone. This group comprises all synthetic oils other than PAO's. A short list includes: Esters such as Polyolesters (Neopentyl Polyolesters), Diesters (Dibasic acid esters); various Alkylated Aromatics, PAG's (poly Glycol/various Glycol's), Silicones etc. This group of synthetics is primarily used for various industrial and aviation applications. Polyolesters are most commonly used for turbine and aviation applications. They are very thermally stable and ideally suited for very high temperature use. Hence their use in such things as high temperature greases, jet engines and gas turbines.
They have a very low coefficient of friction and are sometimes added in small amounts to mineral oils and synthetic oils to lower the coefficient of friction of the finished product. Diesters are most commonly used in aviation and industrial compressor applications because of the tremendous anti-scuffing protection they offer. They are often added in small amounts to PAO-based two-cycle oils as this feature is very beneficial for a two-cycle motor oil. Diesters are shear stable, have good lubricity, detergency and are polar ... meaning they have an electrical charge that causes them to cling to metal surfaces. THAT is a desirable trait for most lubricants. Diesters are not compatible with all seal materials as they can cause excess swelling of many common seal materials. Because of this they are often added in small amounts to automotive PAO based oils to provide positive seal function. Silicones offer wide temperature performance and are sometimes used in compressor applications although this use has fallen out of favor in recent years. More often they are found in high performance automotive braking systems these days. I HIGHLY suggest you do NOT use DOT5 silicone brake fluids. A discussion of why is in my brake and chemicals articles.
Below are a few terms and words used in the petroleum industry, to which you possibly have been exposed-to, but are not very descriptive to laypersons. I am going to mention some of these very briefly here, and if you are interested in a more in-depth discussion, simply do a search by any common search engine, such as Google's.
Before petroleum-based oils became available, back long ago, but even into the 1800's, oils and greases for lubrication came from animal, vegetable, and fish.
MINERAL base oils means petroleum-based oils, from crude oil, or gas, from oil wells sunk into the ground. These types of oils mostly replaced animal, vegetable and fish oils. Oil products are made by several different processes, a few of the major ones are hydrocracking, hydrogenation of various sorts, waxes isomerization ...but, always, the prime method is distillation.
"Paraffins" means the molecules are branch-chains, or straight-chains, of hydrocarbons. I am avoiding the use of the word WAX, here.
"Aromatics" means the molecules are what is called Alkyl Benzenes.
"Naphthenes" are Paraffins in a RING form of molecules.
MOST synthetic oils are made by Polymerizing short chain alpha-olefin hydrocarbons, which are then changed to longer chain types called PAO's. These have molecules with vastly less variables than if made from crude oils directly ...although chemically they are similar in many respects.
Why Choose Synthetic Lubricants?
Motor oils are comprised of two parts, the base oil and the additive package. The synthetic base oil comprises 80-90% of the oil by volume and the additives the remaining usually 10-20%, occasionally more. There are five groups of base oils stated above: Group I, II, III, IV and V. Groups I to III are refined from crude oil containing tars, asphalts, waxes, aromatics & other things. These crude oils are "cleaned up", to the extent possible, by hydrocracking and filtering. The group III base oils are the best of this genre. However, they still contain variably-sized molecules and some contaminants that can result in sludge, varnish and other deposits in your engine. Moreover, the quality of group III base oils vary greatly due to differences in the feedstocks and refining methods utilized.
As a general rule, petroleum-based oils, in the lower Group numbers, require more additives, as much as 30% more. In many instances the cheaper oils are this type, and the additives used are cheaper types. Thus, these oils do not perform all that well for you when you might need or want them to perform. They can burn off rapidly, costing you for topping off the oil. They can fail to perform the truly needed functions of anti-corrosion, etc., as they accumulate modest mileage. In fact, deterioration can begin somewhat above 1500 miles, depending on conditions.
Synthetic oils are group IV (PAOs) and group V (esters) base oils. These synthetic oils are "man-made" synthesized uniform molecular structures that significantly improve the efficiency and effectiveness of these oils relative to their petroleum oil competitors. More specifically, these oils have lower coefficients of friction, better thermal (heat) and pour-point (cold weather performance) properties than do petroleum oils. Synthetic oils have no waxes, tars, or other contaminants to sludge or varnish your engine. Synthetic lubricants are initially more expensive, but may pay off when you consider their extended oil life (and engine-life) capabilities, in addition to their improved performance.
One must be very cautious about using the various Group IV and V oils; they may not be compatible with seals in some vehicles, and as seals are usually made by more than one manufacturer the seal material may not be necessarily compatible with an oil even though the seal has the SAME part number. Still, these are usually THE best performing oils.
If you need ZDDP in the oil; that is, you have an Airhead or very early K motorcycle (and many other motorcycles not just BMW) ...be cautious, be sure the oil has ZDDP, in my opinion at least 1000 ppm, but not over perhaps 1800 ppm. There are other characteristics that are important too. ZDDP is used generically here, as ZDTP is in synthetic oils.
More ...for the even more technically-minded, lots of nerdy stuff too ...on oil functioning ...how lubrication really works, and lots more:
Looking at extremely tiny irregularities in as-machined and broken-in surfaces, a LOW viscosity oil allows the oil to creep into very small microscopic areas. As the load increases, the oil is squeezed between the parts and dynamically increases the oil viscosity; which allows higher load carrying. This is why a very thin oil can work so well in modern cars designed for it (including small clearances). This is why a 10W30 or a 5W30 or even 0W-30, all being very popular or specified now for automobiles, works so well in modern cars (which don't have flat tappet designs, which is a long story). When I say Modern, I am speaking of primarily from the end of the 1980's. Modern engines last a long time due to precise machining, proper selection of compatible materials, expert design for lubrication, improved oils, etc. It is also, in an oblique way, the reason old Harley's, and some other old-time engines, had very thick oil specified. I'm not putting Harley down here, just relating facts. One could say the same thing about many old engine designs ...and some of this applies to flat tappet old performance cars, Porsche boxer engines, and Airheads ...as I described earlier herein.
Oil wedging is a fundamental principle.
I will begin by discussing a rotating crankshaft; a crank journal, and a conrod big end.
The spinning crankshaft does not have equal pressures all around any given bearing surface, as the pressures are not equal over its 360° rotation due to when the piston pushes (and crankshaft pulls) on the connecting rod. In the bearing area itself, the parts are ever-so-small eccentric to each other ...or egg shaped, ...or however you want to visualize this within that tiny perhaps 0.001" bearing clearance. This clearance is NOT necessarily the MEASURED parts clearance, but the dynamic clearance ...more or less.
This eccentricity drags oil into a wedge-shaped layer between the crankshaft journal and its associated conrod bearing, which LIFTS UP THE SHAFT, so the shaft is SUPPORTED by the oil film. Yes, all this happens in that oh-so-thin mechanical clearance; AND, yes, it is true that the eccentric-ness comes mostly during break-in ...so, another reason that break-in oil is changed sooner, rather than at a 'normal' oil change mileage.
Some shafts that rotate inside of bushings are supported by a wedging of AIR ...there is either NO lubrication medium like oil at all! ...or just some to allow no excessive friction as the parts START spinning-up. Most old-time aircraft spinning instrument gyroscopes were like that ...and many turbines work that way (granted, with huge loads and oil to keep things cool). You are probably sitting at a computer screen, and the computer next to you has a FAN, and possibly a HARD DRIVE, that use AIR bearings, to some extent or other. Yes, air can be a lubricating medium. Any problem MIGHT BE only just as the device starts up ...before the bearing is air supported. THAT is usually handled by a very TINY amount of totally invisible lubricant.
An even deeper discussion would describe how oil leaves the wedge at a higher velocity than it entered, followed by a discussion of fluid back-up. Since normal oils can't really be compressed into a smaller volume, its pressure builds up instead; but, this is not intended to be a course on lubrication engineering and fluid dynamics ...so I'm not going to get too deep into these things ...but a bit more ...a bit simplified, is appropriate:
These things about rotating parts also occur in sliding parts ...just not nearly as easy for me to describe and for you to understand. So, no sliding discussions (pun intended!).
In a reciprocating engine some parts are changing direction, a shaft is shifting position, and things move about, perhaps until equilibrium, and the shaft essentially centralizes in the oil film ...well, ALMOST! The oil film is squeezed, forced to move around the shaft, but the viscosity (thickness) pushes back against this change, and that resistance ADDS to the load supporting capability ...up to a point anyway. The high-brow term here is 'squeeze film'.
As rotational parts speed increases, there is a point reached where oil friction suddenly increases VERY considerably. This critical surface speed is where the oil lubricating film starts ceasing to be a laminar flow (layer-like), and becomes a turbulent flow. This is why some race-bikes have oiling failures under some conditions. You can increase oil viscosity, or decrease it, you can change types of oil, you can increase oil pump pressure, you can do all sorts of things including changing clearances ...but, there are limits for each bearing, and many a racer has found those limits! Therefore, just raising the rpm range of an engine is NOT simple for a manufacturer, let alone a racer. Many modern motorcycle engines have very high redline limits for RPM. It was NOT easy for the manufacturer to design and build such engines, and many have very high effective combustion pressures, exceptionally high compression ratios, etc. The pressure on bearings is intense.
Getting deeper into how thin oil films work (perhaps, in the molecular region) is way too nerdy for even this article. I would have to get into what is really meant by oiliness, adsorption, plus more on hydrodynamic lubrication, how the film can be penetrated, and so on. When I studied this sort of stuff, I long kept my notes; and my industry information. My notes were mostly typewritten on both sides of the papers, and are inches thick. Lubrication is a VERY complex subject, AND ...it is still evolving. I have been very interested in the subject for decades.
I probably should quit here. Probably bored 90% of you anyway!!
I'll try to make it simpler from here on....(at least in THIS article). >>>So, what's this ZDDP stuff all about?
ZDDP (or ZDTP) is important for BMW Airhead engines. ALL ZDDP is NOT the same as far as real usage, because there is a difference between a chemical, and what the chemical is dissolved-into, and other nice things. Zinc dialkyldithiophosphate is both an antioxidant (you almost never hear about THAT) and an anti-wear agent (which is not 100% exactly true), and most formulations are somewhat volatile.
As the oil standards specified by car makers and the SAE went from lower to higher letters (SG to SM, as example), the oils had less ZDDP. Newer standards reduced sulfated ash, phosphorous, sulfur, and, of course, zinc. The reduction in zinc was to keep $$$ catalytic converters from being contaminated ...which reduces or eliminates their prime function. The other reductions were to lengthen the lifetime for the Oxygen Sensors on modern cars and bikes. Think about what I just said about oxygen sensors. You DO know that your K1100, etc., has one? Yes, that means you do not want a high ZDDP level for K bike oils, but you need SOME on the earliest of the K bikes (1983-1986) due to their design, which was changed in a few areas, and not really advertised as such for lubrication purposes. Thus, use of ZDDP and ZDTP in Classic K bike oils is a trade-off. I suggest medium-high levels for a very early Classic K bike.
Most SM oils still contain some ZDDP, but in a less volatile formulation. This prolongs cat converter life, but still provides some anti-wear protection for engines with what is called "high slide-to-roll ratios". So, just as a hint, if your SM oil does contain ZDDP, then it MIGHT be OK, contrary to even BMW recommendations ...but you need to KNOW. Getting the information, which includes the ZDDP concentration, is VERY UNLIKELY to be obtained from reading the container printing.
Oil drain intervals, uncommonly known things....etc:
Also See article 51B, https://bmwmotorcycletech.info/oilcansimple.htm
Drain, or oil change intervals are vastly misunderstood. My information comes from REAL industry experts/engineers, not just my personal guesses/opinion/etc. Car makers tests show that drain intervals of 7500 miles are usually OK, even higher mileage for changes in some instances; except in 'severe' uses, which is spelled out as to the meaning. NOT NECESSARILY SO for your Airhead, especially with conventional dino (petroleum) oils. Oil deteriorates from high heat in air-cooled engines (particularly around the valves areas) at a much faster rate than in water cooled engines.
Here is something this is hardly widespread knowledge: Fuel economy decreases quite a bit after about 4000 miles ...as the protective anti-friction additives boil or burn off.
Popular belief is that ZDDP "protection" does not even come into play until things are awful (such as metal-to-metal) ...this is not so.
ZDDP provides anti-corrosion protection, not just friction protection.
There are quite a few things that degrade oil over time and mileage. This includes fuel dilution, contamination from combustion byproducts that escape, typically through rings leakage; incomplete scavenging of crankcase vapors; oxidation, and the shearing action of the engine's mechanical parts. For water cooled vehicles, it takes very little in the way of a cooling system malfunction to shorten oil life ...a stuck-open thermostat is one of the worst things to have happen ...the engine cooling water runs too cool, and so does the oil. For air-cooled engines, the heat around the base of the exhaust valve (spring area) can be so hot that oil passing by this area is degraded rather quickly. Since only a small portion of the entire oil supply passes by that area in a time period, the degradation is slow.
I have mentioned how changing oils TOO OFTEN is not usually a good idea.
Some, in total disbelief, have asked for proof of "Snowbum's crazy ideas" .......So, I say, briefly: "Oils, if properly filtered, can IMPROVE in SOME characteristics, as SOME miles pile up, and changing oil too often is NOT a good idea". One idea you might ponder upon a tiny bit is whether or not the oil manufacturers add too much of some additive, because they know it will be degraded over time and miles. For just one of a number of articles on this oil change interval subject: this article shows that oil may work better AFTER considerable miles since the last change:
https://www.sae.org/publications/technical-papers/content/2007-01-4133/
Obviously, there are limits. Viscosity improvers and MANY other additives may be depleted too much, if you extend oil changes too far. That means that 20W50 oil for your Airhead might be something very different after enough miles. If you had a motorcycle with the GEARBOX being lubricated by the engine oil, things can be much worse for the oil, as the gears WILL shear the longer-chain-molecules of the oil fairly fast. This changes the viscosity, but also has unpleasant effects on other oil qualities. Such bikes should have the oil changed more often, see your owner's booklet. Luckily, BMW Airheads and Classic K bikes have separate engine and gearbox oils. However, SOME oil shearing does occur on our bikes.
Note that for engines being overhauled (or having top end work) and being freshly broken-in, that I do suggest that the oil be changed after a few hundred miles....and the oil filter element be inspected, etc.
In general, for BMW Airheads, and most situations, a 4000 mile change interval ...provided it is at least yearly ...is OK. You might even go longer in time and mileage, particularly if you use a high quality synthetic or part-synthetic such as Spectro's or Mobil 1 in motorcycle viscosity grades. Sometimes twice as long. Worn engines need oil changes sooner!! Diesel oils have a lot of detergents and dispersants in them, to deal with the soot and particulate formation and greater level of crankcase gases. A quality diesel oil, with ZDDP, may still be a reasonable answer to someone wanting a relatively inexpensive oil for their Airhead ...but I can no longer make specific recommendations ...as I no longer try to keep up with changes to them; which are hard to get details about anyway.
Another concern for oils is the moisture that collects in oils in engines that do not come up to proper operating temperature on shorter rides. This is very particularly so with dino oils. If your typical ride is under 20 miles in cool and/or high humidity weather, and certainly if under 6 miles in any weather condition, you should consider changing oil sooner rather than later. Vehicle makers used to include these types of usages in owner's manuals as being under the 'severe service' section. Another factor is the amount of sulfurs in the fuels, which varies by season, country, manufacturer, etc., for which you will have a nasty time finding out about ....but this factor is typically not severe ....but it DOES have cross-reactions with the moisture in the oil ...so, short rides = not good.
The following is for a BMW Airhead motorcycle:
If you are going on longer rides, say over 40 miles in mild weather, and most of your riding is on such longer rides, and seldom quite short ones, you can likely safely extend oil changes. In some instances even two years and 10,000 miles, but this would be about the LIMIT, under very best conditions, and would be for a motorcycle specific, high quality, full synthetic oil, stock pleated-paper air filter, and a motor in excellent condition through-out. For a high quality part-synthetic, such as Golden Spectro 4 in 20W50 or 10W40 grades, I advise changing oil at not over 1 year and 5000 miles, but SOME riders might be able to go a bit longer ...to 7000. See article 51B.
Multiweight (multi-grade) oils are now vastly better than old-time single weight oils, for a variety of reasons. Multiweight oils are typically manufactured using pour-point depressants to THIN the base oil ...so it flows and pumps easily when cold. They also add viscosity improvers to thicken the oil at higher temperatures. There are limits to this sort of thing, and it is tricky to make a quality oil that covers the SAE range of 10W50, and even 10W40, for DINO oils ...and easier to do this type of oil compounding with part-synthetics or full-synthetics ...which, naturally, cost more. Even back to ~1990, it was difficult to get a good 10W40 oil was (the standard was 10W30 for cars); today we have SOME 10W50 oils that are fairly good. Turbocharged cars often have very strict requirements for oil change intervals, and type of oils. Airheads have special requirements due to camshaft and follower design, and, these engines are air-cooled and exposed to a highly variable and wide range of temperatures.
It is the HEAT at which the oil is exposed to inside the engine that for the most part degrades the oil ...besides moisture and your usage. After enough time and miles, the oil degrades a considerable amount.
The Europeans usually have tighter specifications for their oils ...especially car oils ...than we have had here in the USA. The present Euro specification that is tighter and more strict than what is in the USA, is probably ACEA-A3/B3. Look for it on some products in the USA nowadays. Do NOT use the latest CJ-4 oil, as it is only so-so for our bikes. I won't get into it any deeper in this article, it will only confuse you.
Very Specific Oil Recommendations ... and COMMENTS ...For AIRHEADS:
For Airheads, due to the variability of some heat-treated parts, and due to the type of cam and followers; I recommend only the following oils. NOTE THAT THESE ARE NOT LISTED IN ORDER OF PREFERENCE, except as noted specifically.
(1) Mobil 1 V-Twin in 20W50 grade. You can usually extend the drain intervals due to this being a full synthetic oil. This oil can be pricey, and I am not sure it is worth the money; but drain intervals, assuming much longer touring miles than city traffic miles, could be long. This oil has quite adequate amounts of ZDDP or ZDTP, & is a good formulation in all respects. I have one big reservation about this oil IN AIRHEADS ....you might get some leakage at the seals; and lifter rotation tests are not available. Only some few have reported seal problems. I have not used this oil myself in my Airheads. A better substitute is Spectro's Platinum full synthetic, which seems to be well-compounded, with no seal problems in Airheads.
(2) Mobil 1 (not the V-Twin version) in 15W50 is probably usable, but I can't give a blanket 100% OK. BUT, if you want to use a full synthetic, this is likely one of the better ones (see #1, above). Wall-Mart often sells this oil in large containers at a good savings. If you want additional metal scuffing protection for an Airhead, use (1), above.
(3) Golden Spectro 4 in 20W50. A no-nonsense premium oil, it can have somewhat extended drain intervals, as it is a part-synthetic and is well designed and compounded. I have considerable experience using this oil. Excellent quality & has an excellent base stock. It is my favorite over-all Airhead engine oil. It's formulation has remained constant for decades. There are NO seal nor deposits problems with this oil, on ANY Airhead, of ANY year. I also know of NO lifter problem failures.
(4) Golden Spectro 4 in 10W40. Same comments as (3) above, but use only when the initial startup weather is almost always going to be under perhaps 40°F.
(5) BMW 20W50 NON-synthetic motorcycle oil. A good oil, not as good as the above oils.
(6) BMW's present day full synthetic oil: I don't have experience and enough information to comment further.
(7) Valvoline 4-stroke motorcycle oil, in 20W50, or 10W40 for cold areas. Not quite as good as (1) to (4), but good enough. Phosphorus content is 0.103%; calcium 0.182%; zinc 0.112%; sodium 0.052%. For those not wanting to chance seal problems with Mobil 1 versions IN AIRHEADS, yet wanting a less expensive oil than the BMW or Golden Spectro 4, this might be a good choice.
(8) Shell Rotella-T in grade 15W40; calcium 0.27%; zinc 0.135%; phosphorus 0.120%. This is a good oil, can be purchased at a savings in larger than quart sizes. It is often referred to as a 'diesel' oil, which it also is. It is possible that the formulation will be changed, but that is the latest laboratory test information I have on it, and due to those tests ...which also cover other qualities of this oil, I STILL think it likely quite-decent-enough for Airheads. This comment was made in October 2012. I have no plans to test or delve into this oil again. If interested in using it, check with the manufacturer to see what the present ZDDP content percentages are.
(9) DELO 400 oil contains 0.119% phosphorus and 0.148% zinc. Last time I looked the spec sheet was showing those values, and dated in 2011. It has always been a good oil. Same comment as in (8); EXCEPT that I think the other additives make Rotella-T a better oil than Delo 400.
(10) I do not recommend Castrol motor oils EXCEPT for Castrol's 4T oil, (and Grand Prix oil, which is the SAME OIL) in grade 10W40 or 20W50, as appropriate to your climate. These oils are SG rated and formulated. At my last check, Zinc component is 1100ppm; Calcium component is 1900 ppm; Phosphorus component is 1000 ppm, & the detergent and anti-corrosion ingredients were "adequate".
General notes for the above section:
DO NOT use "energy saving" (so marked, and probably have starburst symbol) car oils in your motorcycle, particularly NOT in Airheads. You can use them in an emergency.
If you make mostly short trips under 10, or maybe even 20 miles, change your oil every 3 or 4 months and at 2500 miles. If you ride now and then for over 20 miles (especially well over), you might be able to extend the changes to 6 months ...or even a year, and 3500 miles. If using PART synthetic oil, such as Golden Spectro 4, you can add a few months or so. If using FULL synthetic oils, doubling the recommendation is possibly OK.
The Euro specification that is tighter and more strict than what is in the USA, is ACEA-A3/B3. Look for it on some products in the USA nowadays. Do NOT use the latest CJ-4 oil, as it could be only fair for our bikes, and it is very difficult to find CJ-4 oils that actually have the proper ingredients and amounts, such as ZDDP.
Remember, if you use synthetics, that they are NOT all the same! Be SURE yours has ZDDP or ZDTP, and an appropriate amount, for your Airhead.
***Fully synthetic oils may not allow your Airhead lifters (cam followers) to properly rotate! I have NO direct experience! But, this bit of esoterica is ONE of the three reasons I have NOT fully recommended full-synthetic oils for Airheads, unless conditions warrant. I believe the oils I have recommended, above, are OK in this regard.
Classic K bike engine oil recommendations:
This applies to K1, K75, K100, K1100, K1200
Because of potential $$$$ problems with the starter sprag clutch, and some other things, I am recommending ONLY FULL SYNTHETIC OILS for the engine. The owners booklet has a chart of the recommended grades. If you have an early K bike, the recommendations in the owners booklet may not be up to date.
https://bmwmotorcycletech.info/viscosity.htm has (scan way down) an up-to-date chart for temperatures you expect to start the bike and to ride in, versus viscosity grades. I suggest you do not use the widest ranges unless needed. This chart is OK for Airheads too. My recommendation includes Mobil 1, and you do not need the V-Twin version of Mobil 1, but if you have a 1983-1986 K bike, the V-Twin version of Mobil 1 oil is better for your engine. Spectro Platinum is also recommended. For the Classic K bikes, use any quality oil filter brand, but none with exterior labels that might come off. FILL the filters with oil before installing. The filters are installed upside down so having drain-back valves is not important in them. Fram filters are not recommended.
Use BMW premium oil filters in your Airhead. The two-part hinged filter is recommended. If you have difficulty installing the filter, snip the halves-link.
DO NOT use K & N air filters! If you want to know why, see the K & N filter article:
https://bmwmotorcycletech.info/K-and-N-filters.htm
YES, there IS a reason to also NOT use K & N AIR filters! I recommend no K & N filters of any type. I recommend no Fram filters, this is particularly so for the more critical oil filter, and doubly so if you are using a part or full synthetic or are not changing filters often.
WHY a mention of an AIR filter in an OIL article? ...because ordinary atmospheric air is somewhat (to 'considerably') 'dirty', and those contaminants often are very hard microscopic particles, and CONTAMINATE THE OIL, and DO excessively wear your engine.
ZINC ....ZDDP ...ZDTP ....'special' break-in oils, etc. ....expanded section:
Just what really is ZDDP ....ETC.?
ZDDP is zinc dialkyl dithio phosphate. ZDDP was originally developed in 1930 & introduced for the purpose of oxidation stability in engines with plain bearings ...protecting the copper-lead material. ZDDP still has that purpose, but it also has at least one other use; the one YOU have probably heard about. It is usually thought-of as the lubricant of last-resort, when two metal surfaces rub each other ...and the 'protection' begins just at or around the time actual metal contact is about to, or does begin, that is, the oil film is failing to protect as intended. Much of that is not fully true. The wiping action of cams & tappets are, or can be, yes, particularly hard on materials, and we want protection with our oils. YES, ZDDP (or ZDTP) is in the oil to prevent oil film failure (or give protection if the film fails). ZDDP has other characteristics, and its protection really begins long before real metal contact begins. I earlier in this long article mentioned some of the ZDDP/ZDTP characteristics and why JUST thinking about it as The Last Resort protectant, is WRONG. I'll get a modest amount deeper into it here.
Yes, it is true, that that ZDDP has excellent anti-scuff properties. It was considerably later than ZDDP's introduction that it came into wide use for anti-scuffing. In the 1960s, high performance flat-tappet camshafts were common. It was found that a zinc level of 0.07% was very helpful. Back in the 1960s, all new camshafts were generally phosphate-coated, and together with the ZDDP in the engine oil, the brand-new camshafts and lifters were protected from premature wear, particularly during the critical break-in period. As engines became more powerful, and pressures on parts increased, the level of zinc was increased to 0.09%. Oils changed too, becoming much more complex, and additives for friction modifications, antioxidants, detergents, etc., became common and more sophisticated. Fuel economy began to be of some concern, and the zinc content was continually increased, with premium and super-premium oils commonly having as much as 0.2% ...into the 1980s and 1990s.
Zinc Phosphate is not really any sort of what you might want to call a direct lubricant ...UNTIL IT GETS QUITE HOT. When two metal surfaces rub each other, the microscopic top layers can be extremely HOT, yet the part be quite cold in comparison. This is another of those not easy to understand things.
The actual way ZDDP works is not easily found in literature; and when you do find it, it is highly technical. I will make it simple to understand. When it gets hot at the surface interface, it creates a phosphate glass on the surface. Extremely thin, but it is there. It has been compared to a painter's primer coat. The engine oil is the top coat in this scenario. YOU NEED A HIGH LEVEL OF ZINC DURING BREAK-IN TO ESTABLISH THIS PHOSPHATE GLASS COATING. You also need an adequate amount of zinc for long-term cam, followers, etc., protection, even after the glass layer is initially established. It is well recognized (within the performance engine builders community) that a high ZDDP level is very beneficial for roller camshafts, lifter bodies, lifter bores, roller rocker arms ...especially where high spring pressures are used at the valves ...not just flat tappet applications. Modern CAR oils with little or no zinc (zinc poisons catalytic exhaust converters), use substitutes, often phosphates. Airheads have parts that vary in factory hardening, so some have had no problems using car oils. If you try that, you are the test pilot for your engine.
In the prior paragraph, that I said a high level of zinc during break-in was needed to establish the phosphate glass coating. You may have gotten the idea that zinc might keep a new top-end (such as rings) from properly breaking-in. No, not true. I highly recommend against using special break-in oils, unless you have a very high performance engine, need very quick break-in, ...and are racing it on the track ...or going to put it on a dyno immediately ...even then, you need more information about the oils you propose to use.
ZDDP, in sufficient amount, ensures establishment of that glass-forming coating at break-in. It is quite microscopic, and it is repaired or re-established, however you want to think about it, as the vehicle is used. How well it is repaired or re-established, depends on how much exists after some mileage. Because the additive 'burns off', the best motorcycle oils have a goodly dose, but not too much, when you purchase the oil.
ZDDP or ZDTP is also helpful for K bike engines, particularly the very earliest K100 model, which had some places with different metallurgy, such as different cam characteristics, etc. FEW know about that, for the K100.
ZDDP protects valve tips and pushrod tips. Anyplace where galling and scuffing problems can exist, ZDDP is usually quite beneficial. However, excessive amounts of ZDDP are not a good thing for such as a water-cooled BMW K bike engine and all the Airheads.
It is not zinc, but phosphorus content that is the biggest item of importance in ZDDP, as far as wear from rubbing/scuffing goes. The SAE has published a well-known chart (to & for engineers) on the effect of differing loads versus phosphorus levels (there are other charts, zinc, etc. ...not important right here). Most of these types of charts (there are a lot of them) are presented as lifter loads, in pounds, versus ZDDP or phosphorus, and the criteria is scuffing of parts.
What is particularly interesting about the charts is that the curve is not linear, particularly so at lower concentrations of phosphorus. At lower loadings, only a concentration of maybe 0.03% is needed. At higher loadings ...which occurs with high lift cams or high pressures or both (easier to think of as high performance engines) ...concentrations of 0.08% are needed. More than that amount is required, due to burn-off of the additives, and for a safety factor. Additives cost more than the oil stock does. You can read into that fact quite a lot. You can also think about the fact that it takes zinc to establish the proper glass layer from the phosphorus (phosphates), and zinc is bad for cat converters ...so oil mfrs make compromises, and those are not necessarily good for your Airhead motorcycle.
One last thing on this concentration business. Way excessively more than needed is not good. The charts show that if the Phosphorus concentration goes over 0.14%, then wear starts to increase. At 0.20%, wear is definitely accelerating fast. This means that there is an optimum range of ZDDP formulations and concentration (and, for the revised modern car oils, the phosphorus concentration in particular). That is why you will see that many makers of motorcycle oils keep the phosphorus component down to ~ 0.12% ....that is the same as saying 1200ppm. Some very pricey specialty oils are made with very high concentrations. They are marketed for special break-in purposes primarily. I am not at all in favor of these for your motorcycle. The prime purpose of using these specialty oils is for racing, where extremely fast break-in is needed at times for the ultimate maximum possible horsepower, etc. ...and, do note how often these engines are overhauled! There is a section, later in this article, that gets deeper into these specialty oils, for the curious.
ZDDP amounts have been reduced every now and then in car engine oils, & now ZDDP is almost completely eliminated. That is because the additive contaminated the $$$ catalytic converters. In the early stages of reductions, phosphorus limits were lowered to 0.10%, and zinc levels were dropped also ...but quite long ago. In 2004 came the so-called Tier 2 emissions standards, and OEM warranties changed to 10 years or 100K miles, and phosphorus dropped again, to 0.08% ...and zinc went down to 0.09%. The levels are much lower now ....or, gone.
Repeating it all succinctly here, it is the phosphorus that gives the protection, but it requires zinc to establish the glass layer. For cars, it is the zinc that is damaging to the catalytic converter. That means that car oils with the lower or no zinc formulations, do not allow formation of the full phosphorus glass protective layer needed in our Airhead motorcycle engines, no matter how much phosphorous is in the oil! If you do not have both the zinc and the phosphorus, you will not obtain the proper protective glass layer.
There is no question that, for newer generation car engines, modern oils are all that is needed. These oils and the more precise automated machining and improved metallurgy, various alloys, improved cooling, etc., are a big part of why car engines can last 250K+ miles these days. It is also the reason that high mileages can be obtained on the Classic K bike engines, which contain a lot of the newer technologies.
Coating or otherwise establishing protective layers or very hard layers on cams and followers, is dealt with by many small changes in modern engines. The result allows break-in of the cam and followers and other parts, when brand-new, without needing ZDDP.
Zinc and phosphorus are both needed continuously in Airheads; and if the cam, etc., was not heat treated well-enough, or perhaps not broken in properly, deterioration will begin, sometimes rapidly, upon using the wrong oil. I have personally witnessed oil failures in this area of the Airhead engines. High valve spring loads worsen problems. In a nutshell, EPA regulations, SAE and engine makers and car makers have all 'conspired' against the type of oil you need for your Airhead. Luckily such oils are still available. Yes, there are those who have not used those very good oils and have gotten away with it. I have already explained why that happens sometimes.
One of the reasons for the availability of the oils we need (besides specialty makers of 'motorcycle oils') is that there are those quirks in the rules that I have talked about, which recognize only certain viscosity grades as 'car oils'.
There is a an article on this website, https://bmwmotorcycletech.info/break-in.htm that covers a lot on how to assemble & break-in an Airhead engine, etc.
There is some information on oils, with the heading title of "Information on acceptable engine oils:" in this linked article:
https://bmwmotorcycletech.info/oilcansimple.htm
I suggest you come back after finishing this article, below, and read that one.
Racing, break-in, specialty oils, long-term storage, etc.:
Some, particularly in racing, or maybe just extra cautious folks who have quite old or antique vehicles, may use a dedicated break-in oil with a ZDDP additive; they may also have used a coating on the cam, etc., during assembly, for extra protection at first start-up. I have been asked about this subject, and about long term storage many times, so thought I would put the asked-for information here. Sometimes folks own vehicles that are very seldom used, perhaps are used almost exclusively for shows, or, you name it. These folks almost always know that their oil needs are different, particularly with regards to anti-corrosive additives, etc.
A non-detergent break-in oil could be a straight 30W or even a multigrade, such as a 10W30. You could add a ZDDP additive. You do not have to do that, but do consider what parts of the engine you are breaking-in.
Your regular Airhead engine oil, for normal riding, needs to have AT LEAST 1000 PPM of ZDDP. I've discussed that earlier, and made note that an excessive amount of ZDDP can also be bad. I don't get much into, in this section, the mild mineral oils that one can still purchase, and that some recommend for break-in, because they are generally not needed, and probably not a good idea, unless you KNOW the ZDDP levels for the particular oil. Many of these oils have NONE!
Many diesel and fleet oils contain adequate ZDDP, and many will break in their engines on those.
There are arguments for and against the use of synthetic oils for break-in. In my opinion, it is STILL wise to NOT use 100% synthetic oils for break-in. I have had NO problems breaking-in overhauled Airhead engines with Golden Spectro, a part-synthetic.
There are specialty oil makers who have oils specifically compounded for use in flat tappet engines, for break-in and regular running. So, for those with higher levels of curiosity; ...and do keep in mind that I recommended earlier in this article that you do not use super high ZDDP oils as there are problems with using too much ZDDP ...below is information for reference purposes:
Joe Gibbs oils:
(1) They have a special purpose break-in oil, with 2800 ppm zinc. This oil was developed for quick break-in, particularly for dyno runs after changes made internally to the engine and testing is desired, without normal type of break-in, which may not be reasonable to do under these circumstances. This particular specialty oil is often used where the oil is preheated, the new engine started, and is put on the dyno right away. Be careful about which oil from Joe Gibbs that you use!
(2) They have a Hot Rod Oil, with 1200 ppm ZDDP, in 15-50, 10W30, etc. It is LOW detergent ...did you know that HIGH detergent levels can wash-away the ZDDP somewhat? (Yes, regular CAR oils have HIGH detergency). This Joe Gibbs oil has extra additives for especially long term storage for classic cars ...extra rust protection, corrosion protection, etc. One change a year for the typical classic car show type use. The Joe Gibbs MicroZol BR and BR30 are good oils, if used for the design purposes. The Hot Rod Oil is good for long term storage.
Brad Penn: American Refining Group makes Brad Penn Racing oils. They offer a straight 30W oil with high levels of zinc and other antiscuff additives, called Penn Grade 1. ...specially formulated to help rings seat fast.
Royal Purple: Makes an Engine Break-in Oil. I've not contacted them for details.
ZDDP additives from such as Comp Cams (159 ZDDP additive).
Red Line: has a high-ZDDP break-in oil additive.
Trick Flow TFS-9400.
Eastwood 50332Z.
Isky Racing ZDDP PLUS.
Do you need, or should you use, any these above super-special oils: Probably NOT, unless you have very special conditions or situation.
Miscl. section:
***A GOOD rule of thumb for decades, and still good, even with the naysayers, is that you should not use a full-synthetic oil for break-in ...especially if new piston rings were installed or a fresh cylinder boring or honing job.
Full synthetic oils may not allow your Airhead lifters, even the rings, to properly rotate. I have NO direct experience, but, this is one of the three reasons I do not recommend full-synthetic oils for Airheads.
For Airheads: Some past and faulty 'wisdom' was that the cam, rings, etc., will be broken-in within 500-1000 or so miles, and then you were supposed to switch to a decent ZDDP-containing non-break-in oil. I recommend you do the first start and the break-in the Airheads on one of my recommended oils. I use Golden Spectro 4 (a SEMI-synthetic) usually in 20W50, rarely in 10W40. Break-in an engine that is newly rebuilt, or overhauled, or a top-end has been done, according to https://bmwmotorcycletech.info/break-in.htm
If you wish, go ahead and coat your cam, etc., with a good ZDDP protectant, during overhaul/assembly. If you are going to have the heads and cylinders off for a long time, perhaps awaiting them to be done by your favorite Wrench, I suggest you coat the cam and followers.
***Under NO circumstances, except an emergency (running out of oil? Only oil available is a car oil?), EVER use a car type engine oil if the container has a API starburst Energy Saving symbol, or, says Energy Saving. NEVER EVER for break-in ...and try to never use it at all.Cam lobe profiles differ from engine design to engine design. Some cams have relatively a fast acting 'ramp', some do not, and some have lobe characteristics that are very hard on oils. Cam lobes may look identical to the casual #1 eye-ball, but they may be vastly different, even when they look the same, right next to each other. Cams and followers/tappets also vary in heat treatment. It is my belief that oil film failures seen on some Airheads, and likely on a few very early Classic K bikes, are, at least partially ...and maybe the major cause ...due to the variability with the cam and followers heat treatment. I know of some motorcycles with vast mileages, run on cheap car oils, that have had no problems. I know of failures from common car oils. Note that 'energy saving starburst marked' oils have been on the market long enough, I think, for enough problems to be reported on motorcycles. I do think we will see more and more problems reported as unknowing owners use car oils. I think this will slowly accelerate as more riders do their own maintenance on old bikes, and use the cheaper car oils, for either convenience or cost or both or because 'they just don't know'. What you will likely see with the oiling failure is scored cams and followers/tappets, possibly microscopic (to larger) cracks in the surfaces. Actual engine failure will occur on some engines.
ZDDP versions 'activate' at differing temperatures, and by temperature I am not referring to crankcase oil temperature as much as I am referring to near-contacting surfaces. Differing versions of ZDDP are used in heavy-duty diesel engine oils and different versions in synthetic oils for compatibility purposes. There are real reasons why engines are specified for various oils. BMW said to not use certain oils. There are numerous European (and "Japanese") specifications for oil, as well as our U.S.A. SAE and API folks, who, together with the oil companies and the car makers, have their own specifications for contents and labeling. There are "substitutes" for ZDDP used in many, if not most, modern oils. They are not adequate for some engines, such as our Airheads.
For a vehicle out of warranty, it is the owner's choice as to the brand, type, and grade of the oil. You may ...or may not ...get away with using an unapproved type of oil in your engine. This applies to cars, trucks and motorcycles.
Classic K bike engine internals have a deservedly good reputation for not needing attention, other than oil changes and rare valve clearance adjustments, for huge amounts of miles ...no matter the oil. This is likely changing, and will likely change again in the future. The Classic K bike really should have a good 100% synthetic oil ...you will 'burn' less, and have much less-likely problems with the starter sprag clutch, a pricey repair job.
Zinc, phosphorus, etc. content is expressed as a percentage or parts per million. For engines that really should have ZDDP in them, I believe that concentrations near 1500 ppm are likely optimum, and over 1800 is not needed and detrimental, and under ~ 800 is not nearly enough.
What oils do Snowbum use? I settled on one trusted oil for Airheads so I have not used any other oil in my Airhead motorcycles for decades: Golden Spectro 4 in grade 20W50. I use only one oil for my K bike, a synthetic, Mobil 1, in grade 15W50. I don't bother to differentiate between the several Mobile 1 types, extended or not, gold cap or silver cap. I sometimes get it from Wal-Mart in gallon or 5 quart or liter jugs when they have it. Mobil also makes a 20W50 V-Twin oil, that one is good too (Airheads also), but I prefer a 15W50 for my K bike, and the protection levels of the additives in the 20W50 V-Twin is likely overkill for my K1100LT (maybe not overkill for the 1983-1986 K models), but very good for the Airheads. These are hardly the only good (IMO) oils available. Should the day arrive when I couldn't easily obtain Mobil 1, I would use Spectro Full Synthetic in my K bike. For my car, a 1997 Nissan Pathfinder (I am writing this update in March 2024!), I still have that SUV as my daily-driver, and am still using a common car oil, energy saving, with the API/SAE starburst seal, in 5W30, which works fine for the lifters and weather conditions I live in, year-round; and, you-guessed-it, it's the starburst and grade of oil Nissan recommends, no, it's not Nissan branded oil.
Transmission, driveshaft, rear drive oils:
I generally use 80W90 GL5 petroleum oil at the transmission (and driveshaft on models requiring oil in the driveshaft) and rear drive. Note that dino oil and synthetics are available as 75W90 which are also generally OK, but some full synthetics are not 'sticking' to metal surfaces all that well after some storage time, and because of that, I am generally recommending one use a premium GL5 petroleum gear oil in either of these viscosity ranges. There is some controversy about using SYNTHETIC oils in the TRANSMISSION. I am in the middle of the arguments. More on this a bit further down this article.
Available are much wider viscosity-range oils, such as 75W140; 75W145; 80W140 and 85W140, etc. These extra wide range types in GL5 type are OK under certain SEVERE circumstances, although I have mixed feelings about them. You might consider using these wider range gear oils if you live in the very hottest climates and travel fast, or pull a trailer or sidecar at high speeds; all these types of things being done most of the time. Other than these situations I can not recommend the use of such wide viscosity ranges. Use of extra wide ranges like these can result in strange happenings in both transmission, rear drive and driveshaft. Poorer lubrication in the driveshaft area. Improper spin-down of the gears and meshing speeds in the transmission meaning weird shifting. There may be cold overflowing or poorer lubrication in the rear drive.
Disregard information you may have heard about sulfurs in GL5 being bad on Airhead rear drive brass or bronze parts, because it is not true. That bad information is a hold-over from pre-Airhead days when BMW advised about the changeover on early BMW bikes from engine oil or early versions of gear oil (usually we say GL4) to GL5 hypoid rated oil. From Barrington Motor Work: Chris Betjemann's BMW/2 Motorcycle Restoration and Service Manual (A Guide for the BMW /2 Owner/Restorer); or, check the information out on BMW's own service information bulletin:
BMW AG, recommended lubricant changeover oil to hypoid type GL5 (by Model and Serial number/engine/frame No.):|
R50 |
R60 |
R69 |
|
|
Trans |
646358 |
1814032 |
663565 |
|
Boot |
646486 |
1814032 |
663565 |
|
Shaft |
646486 |
1814032 |
663565 |
|
Final Drive |
641986 |
1814032 |
661445 |
There is one bronze, not brass, shim in the rear drives in the Airheads. BMW specified a GL5 oil. BMW knew what is correct, & I agree. Use GL5 ...NOT GL4 ...in ALL AIRHEADS.
I have changed my recommendations on using only a dino oil in transmissions. My present recommendation is that if you decide to use a synthetic gear oil, it should be of very high quality. It is my belief that it can extend transmission time before overhaul by a considerable amount. At least one other supposedly knowledgeable person strongly disagrees with me, and seems to think that synthetic gear oils decrease reliability; I am not at all convinced. I do know of situations in which a synthetic can be worse, than a dino oil, in transmissions, so, I still prefer you use a dino oil, and change it every 10,000 miles.
DO NOT use Dow Corning moly type gearbox additive in full synthetic oil. In some cases, that additive could be used in petroleum type oil to "try" to improve poor shifting or quiet the gearbox. Be very cautious. Use much less than the containers call for. About 2% (or not over 3%) of Dow Corning M Gear oil additive (again: do NOT use it with synthetic oils), or Guard Dog GD401 for petroleum oils; and same amount of Guard Dog GD421 for synthetic oils (Guard Dog is out of business). Shake the container quite well and use ONLY the concentration I recommend (if you use it) ...and absolutely not the 5-10% Dow suggests on the container. If you decide to try this additive, 18 to 20 cc is about correct for your transmission (~800 cc total oil). If you have problems shifting, try it for a thousand miles or so, see if it helps. If not, you have other problems. ABSOLUTELY DO NOT increase the dose! For the rear drive, you can use about 2%.
For synthetic gear oil I am presently recommending only the Spectro brand, in 75W90, in the type called "Platinum". It can be used in the transmission and the rear drive of Airheads and Classic K bikes. It is OK for the driveshaft on models using oil in the shaft area.
Here is a link to an article about oils, especially for motorcycles. It has some different and interesting viewpoints. It's a bit long, but worth the read, and you may well like the method of presentation: http://motorcycleinfo.calsci.com/Oils1.html
To all of you out there reading this hugely long article: It's your choice.
I have only tried to inform.
Believe what you want.
You will do that anyway.
YMMV.
© Copyright 2024, R. Fleischer
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Last check/edit: Tuesday, March 12, 2024