© Copyright 2013, R. Fleischer
Engine oils, synthetics, additives, and wear, BASICS:
Some additives are
put into base stock oils to help form better 'thin oil films', so the
oil is not pounded-out by impact forces. 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, constantly shearing movements. MOST wear is
from transient loads, such as at the cam lobes.
Regarding cam lobes, the Airhead engine is of the type of engines that professionals describe as having adverse "slide-to-roll" ratios, and of high loading. This type of engine is common to others that have "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 too often well-aware of
failures from wrong types of oils. In particular camshaft and
lifter wear. Today, modern car engines
are so precisely designed and manufactured, that very light oils with no or
limited ZDDP additives can be used. NOT SO with these early engines.
been said about synthetic oils, and mostly it is about how much
better they are than petroleum oils. While based on SOME
facts, many things said are misleading. Especially misleading is that
oil change intervals may be increased GREATLY. While
relatively true (doubling, perhaps) 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). To be fair here, most
modern seals are neoprene or silicon
types, hardly needing specialized swellers. For Airheads, one of the important protective
additives is some form of ZDDP for flat tappet (flat cam follower) type
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. Additives are used for many functions.
When anyone mentions zinc in lubricating oils, they are usually referring to zinc dialkyldithiophosphate, ZDDP, for use in mineral-based oils; or zinc di-thiophosphate, ZDTP, which is normally used in synthetic oils. Both have been used as an anti-wear ingredient in engine oil for many years. The zinc and phosphorus ingredients are most effective when they are used together. ZDDP and ZDTP are some of the many additives that are put into conventional motor oil to improve lubrication qualities.
COMMON USAGE IS TO CALL BOTH OF THESE ADDITIVES ZDDP, EVEN WHEN, TECHNICALLY, THEY ARE NOT THE SAME. FURTHER, SOMETIMES BOTH ARE USED IN AN OIL, OR USAGE REVERSED FROM DINO AND SYNTHETIC. THIS IS PARTICULARLY SO ON SEMI-SYNTHETIC OILS. IN THE ARTICLE THAT FOLLOWS, MY 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 3,000 mile change intervals. It depends CONSIDERABLY on how the motorcycle is ridden....very short 3 mile trips in high humidity perhaps...versus over 20 mile average trips...might be somewhat the extremes to consider...MAYBE...regarding oil changes. Changing 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 the trouble.
There is also a POSSIBLE problem with the word synthetic. Due to a lawsuit (not absolutely true, but best thought of as a lawsuit) won by Castrol (versus Mobil); a highly refined type of petroleum oil, not REALLY a complete full synthetic oil, can, if the manufacturer wished to, now be called synthetic. So-called full-synthetic oils that are on the market may not truly be high 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!
Another problem is that, except for most of the specialty
motorcycle oil makers (who are better at NOT changing formulas), commonly available oils can...and
do.... have their
formulas modified, without the oil makers telling you.
The bottom-line on "synthetic" oil is that for PRACTICAL purposes, if they contain reasonable amounts of ZDDP (for your AIRHEAD bike), they are ALL likely going to be OK and you CAN go further before needing an oil change.
Even the 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. Your Airhead NEEDS ZDDP; but does not need the very high dispersant and some other qualities of SOME diesel oils that might give problems. I simply cannot recommend willy-nilly all modern diesel oils for Airheads. You might carefully select one, but I am not endorsing them any longer. I do think that probably Rotella and Rotella-T, and maybe Delo, are still OK at the time I updated this particular paragraph (April 2011). The ZDDP is not all that needed on Classic K bikes, although the first several years (1983-1986 perhaps) of the Classic K bikes probably do better with a bit of ZDDP in their oils, and ALL engines can actually benefit a bit; but ZDDP is not good for catalytic converters. Modern car oils have little or no ZDDP, as the zinc component of ZDDP tends to poison catalytic converters. Modern car oils are typically energy saving (and so marked), usually are in thin grades such as 5W30,...and are absolutely NOT compatible with your Airhead, and not very good for your K bike either. There ARE some seemingly for cars engine oils that DO contain friction modifiers (Energy Saving oil) that MAY contain ZDDP, and yet are not starburst symbol identified. This happens with such as SOME oil viscosity grades of Mobil 1, since it is made in viscosity grades that are NOT car oil viscosity grades. More information is in my 52B article and my viscosity article.
Thick oils, that is, oils with
higher viscosities, have more internal friction, and CAN support
larger loads....but!...there's always a but!, EH?......HIGH mechanical pressures of/in the parts themselves INcreases
oil viscosity. Yes, that is true; when oil is inside a
common bearing, and the bearing has lots of pressure (think conrods, as
one example), the effective oil's OWN thickness INcreases. This is so
even with the ends of the bearing open. 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 wrong.
A THIN oil is vastly easier to pump and thereby get through the 'system', and INTO VITAL AREAS QUICKLY and will support massively heavy loads. So, a manufacturer uses 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 licks 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 and 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. BUT, today, with
modern fine-machining, 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.
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!
Here is what really happens: The fluid 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 this 'keep the surfaces apart' oil pressure inside the bearing, etc. This is critical when there are slow heavy loads and also for 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.
From what you have read so far, you will understand that you do not want too thick an oil, nor do you want too thin an oil. There IS A REASON that 5W30 or 10W30...and possibly 10W40.....are all too thin (and have other not great characteristics).... for most Airheads
riding in mild temperatures. There IS A REASON that 15W50 or 20W50 oil is most often recommended.
This also applies to K-bike engines.
As parts speed up, other
factors come into play.
viscosity can be juggled somewhat by the engine
manufacturer. INcreasing viscosity will allow more loading,
but then you get higher temperatures; and 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 it 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, which 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
In the very beginning of the K-bike
production, BMW was having
problems with the K bike starter sprag drive clutch not engaging, and finally BMW redesigned it. The newer
type gave less problems, but some problems still remained now and then. BMW offered a full synthetic oil later on. Mobil 1 works quite
well, with VERY FEW reported problems with the early OR later starter sprag
What happened when the starter sprag clutch began
to fail is that it would slip after some sort of
unseen glazing film or wear accumulated; and, perhaps, some loss of sprag
clutch springs tension;...and synthetic oils helped a lot....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 what
is being sold. They do have an oil that was designed for
Harley Davidson's, V-Twin oil.....there have been various names for that oil
over the years. It has a 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, and I haven't made up my mind on it.
Rislone, and a few other additives, perhaps the stronger CD2... used once if needed.... would sometimes free up the K bike starter sprag clutch, which is 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 intense labor, if the cleaning does not work well.
Synthetic and Conventional Oils:
This particular section was plagiarized from several combined internet articles, and highly edited by me.
I claim NO copyright for this particular section. Further, I can't attribute to various authors either.
Oils are categorized in groups by the type of base stock they are made from.
Group one oils. 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 of all-purpose household oil you buy at the hardware store for stuff like oiling door hinges.
Group two oils:
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 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 any farther. Hence the move we see by automakers to synthetic fluids; both in engines and transmission/differentials. Combine that with the need to improve fuel economy (and synthetic lubricants have the ability to do just that) and you can see why "factory filled with synthetic" is becoming more and more common in cars and some bikes.
Group three 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 it is not made from a truly synthesized engineered molecule and as such is not a true synthetic oil (as far as I am concerned!, see just below a couple of sentences), 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" a few 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 sued Castrol Inc. makers of Castrol Syntec, accusing them of marketing a hydro-cracked petroleum oil as a synthetic. Mobil Inc. felt 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 in the synthetic oil market with a oil that was not truly a synthetic product.
In the end though, Castrol convinced the Court 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, manufactures are eager to jump up and grab the profits for sexy-customer-grabbing-word "synthetic" on the bottle. Group three oils do not have the performance of true custom engineered synthetic oils, especially in temperature extremes. As was stated before, the vast majority of what is being sold as synthetic are really Group Three petroleum based oils-and the public for the most part doesn't know the difference.
Group four oils:
Polyalpha olefin 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 is 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 five oils:
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 to 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 it can be 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 the brake and chemicals articles.
Why Choose Synthetic Lubricants?
Motor oils are comprised of two parts, the base oil and additive package. The base oil comprises 80-90% of the oil by volume and the additives the remaining 10-20%. 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.
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 and engine-life extension 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 THE best performing oils. If you need ZDDP in the oil, that is, you have an Airhead motorcycle...be cautious, be sure the oil has ZDDP, perhaps at least 1000 ppm, and not over perhaps 1800 ppm. There are other characteristics that are important too.
All the above should give you pause to THINK, consider, decide (perhaps).
More...for the even more technically-minded, on oil functioning:
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 today for cars, works so well in modern cars (which don't have flat tappet designs), and modern engines last so long (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 had very thick oil specified. I'm NOT putting Harley down here, just telling real facts. One could say the same thing about many old engine designs. ...and some of this really does apply to such as flat tappet old performance cars, Porsche boxer engines, and so on (and Airheads)....as I described earlier herein.
Oil wedging is a fundamental principle that you might want to know about. Let me begin by discussing a rotating crankshaft; a crank journal, and a rod 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 pulls) on the rod.
In the bearing area itself, the parts are ever-so-tiny
eccentric to each other...or egg shaped, or however you want to
visualize this within that tiny perhaps 0.001" bearing
clearance. This eccentricity drags oil into a
wedge-shaped layer between the journal and the 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.
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 a HARD DRIVE, that use AIR bearings, to some extent or other. Yes, air can be a lubricating medium. Any problem MIGHT BE just as the device starts up....before the bearing is air supported.
An even deeper discussion would describe how oil leaves the wedge at a higher velocity than it enters, and then a discussion of fluid back-up. Since oil 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 things...just a wee bit more. These things about rotating parts also occur in sliding parts....just not nearly as easy for me to describe and for you all to understand. So, no sliding discussions (pun intended!). In a reciprocating engine like our Airheads and K bikes, the parts are changing direction, and the shaft is shifting position, and things move about 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 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...a LOT. 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 MIGHT give you some idea about 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!
Getting deeper into how thin oil films work in the molecular region is way too nerdy for even this article. It would get into what is really meant by oiliness, adsorption, more of hydrodynamic lubrication, how the film can be penetrated, and so on. When I studied this sort of stuff, I kept all my notes; and my industry information, and they are nearly 2 inches thick. Lubrication is a VERY complex subject, it is still evolving. I probably should quit here. Probably bored 99.9% of you anyway.
ZDDP is important for Airhead engines. ALL ZDDP is NOT the same. Zinc dialkyldithiophosphate is both an antioxidant and an antiwear agent, and most formulations are somewhat volatile to a bit too 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 reduce sulfated ash, phosphorous, sulfur, and, of course, zinc. The reduction in zinc is to keep the $$$ catalytic converter from being ruined; 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). It is a trade-off.
Most SM oils still contain some ZDDP, but in a less volatile formulation. This prolongs cat converter life, but still provides some antiwear protection for engines with 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.
Oil drain intervals, etc: This is a vastly misunderstood item. My information comes from REAL industry experts, not just my personal opinion. It is true that car makers tests show that drain intervals of 7500 miles are OK, even more in some instances. NOT NECESSARILY SO for your Airhead, with conventional dino petroleum oils. NOTICE ALSO, that ...and this is hardly widespread knowledge!!......fuel economy DEcreases quite a bit after about 4000 miles...as oils burn off the protective anti-friction additives. You would NOT think that could be true, after all, you think (??) that the ZDDP, etc., does not even come into play until things are awful...but it is not so. 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.....and, 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.
I have mentioned how not changing oils TOO often is better...well, 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 the miles pile up, and changing oil too often is NOT a good idea"". For just one of a number of articles on this, try: http://papers.sae.org/2007-01-4133/
Viscosity improvers may be depleted too soon, if you extend oil changes too far. That means that 20W50
oil for your Airhead might be something else.
In general, for Airheads, a 4000 mile change interval....provided it is at least yearly...is probably OK. You might even go a bit longer on a K bike, particularly if you use a quality synthetic such as Mobil 1. If you let your Airhead oil level regularly fall below the half-way position on your engine dipstick, it may be better to change the oil somewhat more often. On the other hand, most Airheads will 'burn off' the first half-quart quickly, so the engine oil level should not exceed the maximum and might be better to be a bit under it. Older worn engines need oil changes sooner. Diesel oils have a lot of 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 the best answer to someone wanting a relatively INexpensive oil for their Airhead...but I can no longer make specific recommendations....as I can't keep up with changes to them; which are hard to get details about. Another concern for oils is the moisture that collects in oils in engines that do not come up to proper operating temperature for a long enough ride. If your typical ride is under 20 miles, and certainly if under 6 miles, that means YOU.
Multiweight (multi-grade) oils are generally 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 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.
The Europeans...as of February 2009.... usually have much tighter specifications for their oils...especially car oils...than we have here in the USA. Those who use Euro oils in their cars can extend changes. Don't, for Airheads.
Oil recommendations for AIRHEADS:
For Airheads, due to the variability (I
think!) of some heat-treated parts, and due to the type of cam
I can recommend the following oils:
(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 longer touring miles than city traffic miles, could be quite long, with safety. This oil has
plenty of ZDDP in it, 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. Only SOME have reported this. I don't use
this oil myself in my airheads.
(2) Mobil 1 in 15W50 is probably usable, but I can't give a blanket 100% OK. BUT, if you want to use a
synthetic, this is likely one of the best. Perhaps, in mild weather, (1), above, is better.
(3) Golden Spectro 4 in 20W50...can also have SOMEwhat extended drain intervals, as it is a
part-synthetic. I have considerable experience with using this oil. Excellent quality.
This oil also has an excellent base stock. It is my favorite Airhead engine oil. It's formulation has
(4) Golden Spectro 4 in 10W40. Same comments as above, but use only when the weather is under
(5) BMW 20W50 NON-synthetic motorcycle oil. This is a good oil, but not quite as good as the above
(6) BMW full synthetic oil: I don't have experience and don't have enough information to comment further.
(7) Valvoline 4-stroke motorcycle oil, in 20W50 (or 10W40 for quite cold areas). Not as quite as good as
(1) to (4) but plenty good enough. The phosphorus content is 0.103%; calcium 0.182%; zinc 0.112%;
sodium 0.052%. For those not wanting to take a chance on seal problems with Mobil 1 versions,
yet wanting a less expensive oil than the BMW or Golden Spectro 4, this might be a very 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 quite a savings, in larger than quart sizes. It is often referred to as a 'diesel' oil,
which it 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 is being made in October 2012.
(9) I cannot recommend Castrol motor oils, of ANY type EXCEPT for: Castrol's 4T oil, (and Grand Prix
oil, which is the SAME OIL) in either grade 10W40 or 20W50, as appropriate to your climate. These
oils are SG rated and formulated. Zinc component is 1100ppm; Calcium component is 1900 ppm;
and Phosphorus component is 1000 ppm.
Do NOT use cheap energy
saving (so marked, and probably have starburst symbol) car oils.
If you make ONLY short trips (under 10 miles), change your oil every 3 or 4 months. If you ride now and then for over 20 miles at one time, you might be able to extend the changes to 6 months...or even a year.
The Euro specification that is tighter and more strict than what is in the USA, is ACEA-A3. 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.
Remember, if you use synthetics, that they are NOT all the same! Be SURE yours has ZDDP, and a goodly amount, for your Airhead.
If you ride a fair amount in rather cold weather, especially below freezing, I strongly suggest a lighter grade than 20W50. 10W40 perhaps. Consider even a 15W50 or 10W50 synthetic.
Avoid the CAR grades....as they will very likely have characteristics that you do
Do NOT use cheap oil filters in your Airhead. Use the two-part hinged filter, if you can.
I will BET that you NEVER have heard of this!.... Too frequent oil changes can INCREASE wear!! I am not going to spell out why, and leave that to your imagination!...but, it is true. Your 'common sense' tells you I am totally wrong, right? ...as noted above, try this (there are other more in-depth articles on this subject): http://papers.sae.org/2007-01-4133/
****DO NOT use K & N air filters!! *** .. if you want to know why, see the K & N filter article: click
ZINC....ZDDP; 'special' break-in oils, etc......expanded section...:
Just what is ZDDP....ETC.:
ZDDP is zinc dialkyl dithio phosphate. ZDDP was originally developed in 1930 and 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. It is 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. For reasons far beyond this reasonably short (??) reply, the wiping action of cams and tappets are particularly hard on oils. Zddp is in the oil to prevent oil film failure (or give protection if the film fails).
It was found that it has
excellent anti-scuff properties. It came into wide use much
much later. 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 oils commonly having as much as 0.2%....into the
1980s and 1990s.
Zinc Phosphate is not really a 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. ZDDP is often called the "lubricant protector of last choice". That means that when the oil film fails, ZDDP should be taking over, giving you some goodly added protection. The actual way ZDDP works is not easily found in literature. When it gets hot at the surface interfaces, 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 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. ZDDP protects valve tips and pushrod tips. Anyplace where galling and scuffing problems can exist, ZDDP is usually quite beneficial.
It is not zinc, but phosphorus content that is the biggest item of importance in ZDDP, as far as wear goes. The SAE has published a well-known chart (to 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 Ph, and the criteria is scuffing of parts. What is 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 high performance engines)....concentrations of 0.08% are needed. What is needed means that MORE than that amount is required, due to burnoff of the additives, and for a safety factor. One last thing on that concentration business. Way more than needed is NOT good. The charts show that if the Ph 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 concentration (and, for the revised modern oils, the Phosphorus concentration).
ZDDP amounts have been reduced in some car engine oils, or completely eliminated. That is because the zinc and phosphorus contaminate the $$$ catalytic converters. Phosphorus limits were lowered to 0.10%, and zinc levels were dropped also 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.
no question that, for modern engines, modern oils are VERY
SUPERIOR. These oils are a big part of why engines
can last 250K+ miles these days. Improvements in
metallurgy and machining, even cooling of parts, and a few other things are the rest of
the story. The BIG
problem is break-in of the cam and followers and other parts,
when brand-new. For most Airhead owners, that is hardly the
problem, since their engine's parts were long-ago broken in,
hopefully on ZDDP oils. BUT, the zinc (and phosphor to some
extent) are needed continuously in Airheads; and if the cam, etc., was NOT
heat treated well-enough, or perhaps not broken in on a
proper oil....deterioration will set in. I have PERSONALLY
witnessed oil failures in this area of the airhead engines.
High spring loads compound the 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 available. One of the reasons for the availability (besides specialty makers of 'motorcycle oils') is that there are a few quirks in the
rules, which recognize only certain viscosity grades as 'car
There is a
break-in article on
this website. Yes, that was a hyperlink. You want proper ZDDP levels in your break-in oil, and still in your regular oil after break-in.
Versions of ZDDP are not all the same. ZDDP itself is generally not used in synthetic oils; a version called ZDTP is used, see near beginning of this article.
Some, particularly in racing or maybe just overly nerdy street vehicle owners who own old 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, so thought I would put the asked-for information here. A non-detergent break-in oil could be a straight 30W or a 10W30, plus a ZDDP additive. Your regular engine oil needs to be AT LEAST 1000 to 1200 PPM of ZDDP. You can also use more common oils and add ZDDP. Many diesel oils contain adequate ZDDP. There are specialty oil makers who have oils specifically for flat tappet engines, break-in and regular running. So, for the EXTREMELY NERDY.....
Joe Gibbs oils...BR and BR30. They have a special break-in oil, with 2800 ppm zinc...!!!...this oil was developed for quick break-in and dyno runs. They have a BR oil in 15W50. These specialty oils are often used where the oil is preheated, the new engine started, and is put on the dyno right away. 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? This oil has extra additives for especially long term storage for classic cars...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.
Brad Penn company. 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 company...makes a Engine Break-in Oil.
ZDDP additives from such as Comp Cams (159 ZDDP additive).
Red Line has a high-ZDDP break-in oil additive.
Trick Flow TFS-9400.
Isky Racing ZDDP PLUS.
Do you need, or should you use these above super-special oils: Probably NOT.
For those that asked:
Mobil 1 has no special break-in or additive, but does make a OW40 with 1000 ppm ZDDP...and, of course, Mobil 1 products that contain lots of ZDDP, such as the 20W50 V-Twin oil; and the 15W50 oil. Some of these oils are listed in my viscosity article, or elsewhere's on this site.
rule of thumb for decades, and still good, is that you should
NOT use a full-synthetic oil for break-in....especially if new
piston rings were installed or a fresh cylinder honing job.
***Fully synthetic oils may not allow your Airhead lifters to properly rotate!! I have NO direct experience! But, this bit of esoterica is ONE of the three reasons I do NOT fully recommend full-synthetic oils for Airheads.
The cam, rings, etc., will be broken-in within 500-1000 or so
miles, and then you can switch to a decent ZDDP-containing
non-break-in oil. Frankly, I don't bother, I just start and
break-in the Airheads on one of the recommended oils in my list above. For me, I
use Golden Spectro 4 usually in 20W50, more rarely in 10W40.
If you are very much a nerd...go ahead and coat your cam, etc., with a good ZDDP protectant, during assembly.
***Under NO circumstances, but an emergency, EVER use a car type engine oil if the container has a API starburst symbol; NEVER EVER for break-in...and try to never use it at all....
So; what do you use for a break-in oil? It is up to you. Frankly, I simply use 20W50 Golden Spectro 4 on Airheads. See my break-in article!
Some closing remarks:
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 nearly identical to the casual #1 eye-ball, but they are often 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 the oil film failures seen on some Airheads, and likely some EARLY 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. '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. 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. 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 some oils were specified for some engines and some oils forbidden in others. This was a problem a number of years ago. There are numerous European (and """Japanese""") specifications for oil, as well as our U.S.A. SAE and API folks (together with the oil companies AND THE CAR MAKERS) ideas on labeling and specifications. 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. 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 for the worse as time goes on, and more use of car oils is made. On the Airheads, it is likely a contributing factor already in some early engine work being needed...and I expect we will see more damaged cams and lifters.
Zinc content is usually expressed as a percentage or parts per million. Either way is OK. For engines that really should have ZDDP in them, my personal feeling is that concentrations near 1500 ppm are likely optimum, and over 1800 is not needed and detrimental, and under maybe 800 or 900 is not enough.
What oils do Snowbum use? I settled on one trusted oil for the Airheads so I have not used any other oils for decades: Golden Spectro 4, usually 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 jugs when they have it. Mobil also makes a 20W50 for V-twins, 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 "Harley oil" is likely overkill for the K. These are hardly the only good (IMHO) oils available. Should the day arrive when I can't easily obtain Mobil 1, I will use Spectro Full Synthetic, in my K bike.
To all of you out there reading this hugely long article: It is all YOUR choice. I have only tried to inform.
Believe what you want.
01/25/2007: slight revisions and editing for clarity. Remove poor formatting.
01/22/2008: edit slightly for clarity
07/12/2008: minor clarifications
07/14/2008: more clarifications
02/27/2009: Update by adding the entire addendum #1, and making minor corrections otherwise, in line with changes by SAE, etc.
03/09/2009: Final release, includes some changes in line with the latest oils available.
11/16/2009: Add last section
01/21/2010: minor updates and clarifications; add script to code
04/21/2010: Add to section on ZDDP
06/18/2010: Updated the airhead oil recommendations to include the caveat on Mobil 1 V-Twin oil, and changed the commentary slightly for the Spectro GS4 20W50
09/01/2010: added hyperlink to SAE article
11/12/2010: slight updating, mostly for clarity and poor grammar.
11/18/2010: add ppm of zinc for 4T oil
02/24/2011: was 52C
04/10/2011: Fix K & N article internal hyperlink and clean up entire article SOME
08/03/2012: Get much deeper into synthetics, etc.
10/12/2012: revise layout; add QR code; add language code; update Google Ad-Sense code; update article contents
11/05/2013: clean up article...still is messy!......clarify a few details...
© Copyright 2013, R. Fleischer
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