This discussion is for oils for BMW Airhead Boxer engines, and not for those with wet clutches, WWII aircraft engines, lawnmowers, etc, etc.!  There is also some good information here for BMW K bikes and Oilheads.

Revised by the Author 11/05/2007 and 11/01/2009 (slightly):
This article has NOT been fully revised!!

Over the years, oils have been a popular subject for discussions in our motorcycle publications and club magazines, and, yes...even
the Airheads List! I am not sure just why that is, but I suspect it has to do with our society of easyfixitus, or 'I need to do something to
 feel good', a panacea for the masses...and maybe male ego, ..and who knows what else! Certainly there is a large amount of placebo
effect here. REAL facts are hard to come by, and so-called 'evidence' abounds, and may be quite difficult to verify. There is a
considerable amount of so-called 'information'. Some is good, some is anecdotal, some based on testimonials, some sort of like
 'my brother told me of his friend who has a friend who told him that...'; or, 'my mechanic who has decades of experience, says....
 Did you ASK that person just HOW he REALLY got that information he is giving you?   Does that mechanic friend have a sweetheart
 'deal' with a particular oil's distributor; has he ever REALLY seriously tested oils in Airheads?   How did he test them?   Has he looked
 at hundreds of cams and lifters?   Do YOU believe the stories often heard...that car oils ARE plenty good enough, you hardly need
pricier specialty oils?    Some information even seems scientifically derived, and implies itself to be definitive. In addition, there is all
 that advertising. SORRY, but those hyped additives like Slick50, QMI, etc., and those tests on TV of engines run without oil....these
are sideshows; you never hear the entire story of the tests.... DO NOT believe these folks. YES, it is true that you MAY have less
friction, higher fuel economy, etc. HOWEVER, you will also likely get much increased WEAR (YES, you can have less friction and
 MORE wear!), the product may settle out or 'clump', thereby plugging oil passages and oil filters, etc. This can lead to oil starvation
and catastrophic engine damage. As for additives like Bardahl or Rislone or Marvel Mystery Oil: don't use them, they can remove the
protective coatings on your engine parts.

OK, have I got your attention yet, have I offended everyone?

In preparing this article on oils, and in updating a few times over a long time, I not only relied on MY background experience, but that
of several very well known and RECOGNIZED experts on Airheads.  I also did a fair amount of research, and I actually did some tests
on pour temperatures, slipperiness, and shearing. I made up some jigs and tests to do this. I spoke to some petroleum engineers!!,
and obtained some off-the-record information. I looked into some specifications not normally available, on additive types, actual
temperature effects on residues, neutralization number (a measuring method and answer dealing with how well the compounded oil
neutralizes acids), channeling (when an oil is so thick at a low temperature that it does not flow at the gear meshing surfaces, and so
the metal is starved for lubrication), shear strength, film strength, shear resistance of the VI improvers (additives), load carrying,
corrosion resistance, foaming problems, detergency, oxidation resistance (oil, particularly petroleum, will oxidize at higher temperatures
and gets thick and flows poorly)....AND, lastly, the one item that I could NOT get the straight & definitive answers I wanted:
seal compatibility.

I paid a considerable amount of attention to lubrication effects and the effect on the lubricants of the high temperatures found in our
Airhead valve areas. We do not have starters or clutches in our oil, and we need good shearability protection in the transmission,
which is why BMW wants us to use GL5 gear oils there...not just in the rear drive (and, PLEASE, disregard old 'stories' about GL5 oils
not being OK for airheads, it supposedly eating into brass parts....  NOT true!!).

FYI: BMW's own oil is/was manufactured by Spectro, and is NOT Spectro 4 or Golden Spectro 4; not that this means TOO much, and
the BMW oil, while OK for our Airheads, was really designed for the Classic K series (the early K models, like the K75 and K100), in
which temperatures are vastly better controlled, being water cooled motors.   Strictly speaking, the oil was not as perfect for Airheads
as it could be, but was quite acceptable.  REAL Golden Spectro 4 was BETTER.

I am not going to go into some of the more esoteric oil terminology, like base stocks, polymers, bright stocks, uptreats, synthetic oil
bases..diesters, polyolesters, polyalphaolefins, alkylated benzene's, etc., and all--or most--of the terminology used by petroleum geeks.

What owners of Airheads should be concerned with are the basics, and that the oil manufacturers additive package is a good one
over-all; one that activates at AIRHEAD temperatures, does not get burned up quickly...that is, is not overly volatile, and that has a
decent amount of a proper, for airheads, ZDP/ZDDP (a zinc/phosphorus compound). This compound is an extreme-pressure, anti-wear
compound.   IT REALLY DOES NOT DO MUCH UNTIL THINGS GET PRETTY EXTREME, LIKE METAL-TO-METAL CONTACT, or
 nearly, WHICH  IS NOT A NORMAL SITUATION, BUT CAN HAPPEN.  ZDDP is the LAST LINE OF DEFENSE, PARTICULARLY
if you like to go up to or near redline rpms, which really does cause excessive wear on our engines. Going over 6500 or so on a BMW
boxer, or perhaps 7300 on a mildly modified engine, is of no benefit at all, particularly in performance; and, I believe, is hard on nearly
everything, including those older alternator rotors when you begin shifting back down (reverse torque on the rotor). High rpm's near
red line wears things out faster...much faster.   It tends to scrap oil films off parts too. That's not exactly correct, but good enough for
HERE.  That does not mean that you should 'lug' the engine by riding at 2500 with plenty of throttle! Our airheads perform really well
between about 3800 and about 6200. You will not hurt the engine by cruising for hours on end at 5000 or so.  It is when you get within
maybe of 1000 of redline and higher, that wear increases much faster.   Zinc compounds protect some metal surfaces at extreme
conditions: high heat, high rev's, racing, etc. The primary protected surfaces are cams, lifters, cylinder bores, piston rings. Once the
necessary amount of the correct version of the zinc compound is present, you get no more protection from more zinc. Note that
excessive zinc can give you deposits on your valves, foul spark plugs, etc.

Zinc has been reduced in the later oils (SJ, etc.), and eliminated in CAR oils in the latest XX letters because zinc damages the catalytic
converters in cars. It only takes a very tiny amount of the zinc to give the proper protective effect. I am in agreement that about 0.11%
is about correct for decent protection, and I also think that .20% is likely pushing the idea, and probably a bit more than needed
...or desired.

I will mention, since the subject does come up now and then, that years ago use of straight weights of oil were recommended,
particularly for severe service, in that the multigrade oils were not as good. This was in the days when the thickeners (OK, polymers)
were not all that shear stable. What happened was that the moving parts tended to 'shear' the oil, resulting in a lowering of the higher
number (the 50 in 20W50, for instance). For quality oils, this shearing problem has not been true in many years...or, is simply vastly
lessened.

An oil that is 20W50, should be thought of as 20W-50, the hyphen separating the two parts. Also, note that in some areas of multigrade
oil types, some are less desirable...10W40 being one instance where I do NOT recommend that, UNLESS it is a SEMI or FULL synthetic oil...with ZDDP.  A 15W40 is not as additive happy, and maybe a good semi-synthetic in that grade would be acceptable.   These oils can be used in colder weather.

There are some FEW who still use single grade oils in BMW's. Usually these folks live in extremely hot desert areas.  Single grade oils
generally are burned up through the valve guides, and multigrade oils tend to reduce consumption at the rings.....are you REALLY
concerned about adding a half quart in 3000 miles or whatever? ...but... what about long-term wear?

I WILL FLATLY STATE THE FOLLOWING: QUALITY multigrade oils are better in ALL respects for
Airheads...AND.. PLEASE...do not add any additives to your oils.

If you often start your BMW below perhaps 20°F (there are SOME who do! BRRRRH!), then it might be better for you to use a full
synthetic oil. If you intend to use a full synthetic oil at all, do not install it until your engine has broken in...probably a couple thousand
miles, where, by then, the rings have very likely broken in properly and oil consumption has definitely stabilized...this recommendation
has not changed over the years. If your engine is getting tired and is burning oil, you may not want to use synthetic oils, although there
may be no actual problems, just usage of a pricey oil.

It is oil degradation that is the MAIN reason that petroleum oils need to be changed regularly, and NOT contaminants from combustion
products. This was not always 100% so, back in the days of heavily leaded gasolines.  Thus the long drain intervals of semi and full
synthetics is likely justified...but NOT over 10 or 12000 miles in one season.

Keep in mind that your BMW oil filter is not designed to be a 'depth filter', the word 'depth' being a code word for long mileage/long time.
HOWEVER, it is almost always OK to change the airhead oil filter at every other normal oil change. The filters are changed at about 500
or 600 miles on a new or rebuilt engine, and ALL removed filters should be taken apart and inspected on both sides of the filtering medium,
a type of treated and pleated paper.   BTW, in general, the HINGED BMW filters are stronger and better; and SOME aftermarket filters are
NOT good and even not safe.

Most engine wear occurs at startup from cold...that is just one reason a multigrade is better....AND, they are better at the high end of
temperatures.

Oils vary CONSIDERABLY in quality, and it is NOT just a matter of the additives! It is the TYPE of petroleum's, the quality and combination
of the additives, etc. Some cheap oils will burn off rapidly, and/or their additives will burn off rapidly.  That means you loose the first half
quart or quart rather rapidly.  Some oils have synthetics added to help avoid this, or to modify other straight petroleum characteristics.
Thus, except for special instances, a semi-synthetic might be the best of all oils for your airhead.  One of the best semi-syn oils is Golden
Spectro 4.   Most airhead owners in mild climates use it in 20W50 grade.

The price of oil, by the single quart (or liter), varies greatly.  The extra money often does not buy you anything but perhaps peace of mind.
There are Diesel engine oils that are, or were, VERY good, because they CAN and DO contain ZDDP and better oil formulations.  Oils like Delo
and Rotella, in standard AND synthetic versions, are or were very good oils.  Many an airhead owner who does not want to pay the $$ for a
motorcycle-specific oil, will use Delo or Rotella.  You can't use Delo or Rotella in a gasoline engined car with a catalytic converter.   These oils are, however, reducing ZDDP content, to be taking effect more and more as the years go by.

I have said this before, and I am basically repeating it here: If you REALLY intend to keep your Airhead for 100K++, use a quality m/c oil
designed and sold for air-cooled motorcycle use...and if you insist on a cheaper oil, use Delo or Rotella.   There ARE reasons to use
these oils.....ZDDP; good base stocks, good additives....and YOUR airhead might be the one with the marginal heat
treatment on the cam and cam followers...riiight?

Regarding Cx oils: I don't want to get into this in depth, BUT, oils GENERALLY come rated on the plastic bottle/can as having BOTH
a CX and SX rating. These oils are OFTEN, but not always, a COMPROMISE. There ARE some very good oils that are rated both SG and
CD, for instance. Keep in mind that the ZDDP additive we want so much for our cam faces, lifters, and cylinders/rings, come in different
grades, costs vary for those, and certain grades work better at higher temperatures and pressures. Some have a wider RANGE of
operating temperature. Of course ZDDP is not the only difference in additive for CX oils. CX graded products are manufactured to
release usable additive at a very high temperatures, and this is not a good idea for Airheads, unless they release at lower temperatures
also. So, you may ask, 'my oil is rated at CX AND SX, what do I do?'....In my opinion, you change to Delo or Rotello (maybe) or purchase
BMW oil from your dealer...or....from a motorcycle oil manufacturer such as Spectro, etc.  Golden Spectro 4, with a very good
additive package, including some synthetics, is what I personally use in my AIRHEADS,,,,but I am NOT pushing this on you, there ARE
others, some cheaper too. I'd be using Delo or Rotella, otherwise...until they reduce the ZDDP under 800 ppm or so.  I would not be a bit surprised if my use of that Golden Spectro 4 oil
was not a bit of an overkill, especially since I change it regularly, and I seldom go to redline. I also think that, for many Airhead riders,
the cheapest oil (even an SJ) will be adequate. However, here is something hardly EVER considered, and probably the root cause
for those anecdotal reports of vast mileages on the cheapest oils:
HEAT TREATMENT of the various metal parts may well vary considerably between any two or more
Airheads. Particularly in cam lobes and lifters (followers).

You should change the oil regularly, even if it is synthetic or has some synthetics. That is MY OWN belief.  I believe it is especially
important if your oil is a non-synthetic.   SEE the paragraph just below for another of my own contrary opinions....that maybe
is not all that contrary.   Change intervals depend on your riding. You all know this stuff: if you do mostly stop and go in town traffic,
or pull a trailer or have a sidecar, or ride short under 10 mile trips where the oil never gets hot enough to burn off the moisture
accumulated;,,,,change the oil every 3000 miles, or so,,,,otherwise 5000 or even 8000+ is likely acceptable with part or full synthetics,
and mostly high speed highway miles. Change the filter every other oil change, inspect it carefully for metallic looking or plastic
looking particles.
NOTE:  I believe that it is entirely possible that a good full synthetic, perhaps one like Mobil 1, which is
often found considerably cheaper than fancy motorcycle synthetic oils, and the Mobil is available in
15W50 grade, ....and I suppose I can add here a full synthetic Delo or fully synthetic Rotella-T....can be left
in an Airhead engine for up to maybe even 2 or 3 years, if mileage is under 12,000; and stop and go riding
is at a real minimum; and not long after stop and go, one does a ride over 20 miles.  I have NOT proven
this by any real world nor laboratory tests. It is possible there are many other full synthetic oils that are
just as good, even better.  I just do not have the data to prove this idea of mine.   I don't really recommend
anyone do this, but I HAVE seen what appears to be good results for residual oil on parts after long storage,
and big miles and long times.  As I update this section of this article in November 2007, I am doing very
long term tests (at low mileages) on Golden Spectro 4, 20W50.  This is on one of my own Airheads,
and I intend to stretch the oil change to maybe 4 years, but under 5000 total miles (yes, not a misprint).

Contaminates accumulate in oil between oil changes, no matter what type of oil you use, including synthetics. Some of these oil
additives, used by the oil manufacturers in manufacturing their oils, wear out, and are only replaced when you change the oil.
There really is a limit to the change interval. JUST what that limit is for each oil is not the type of thing you can easily find out.
For sure the manufacturer's will never tell you!  The contaminates accumulate fast at cold startup.  Petroleum base oils have
sulfurs, some more, some less.  They are much worse at this sort of thing than most synthetics.  At startup, moisture
accumulates in the oil, and tends to create acids with the sulfur. Acids EAT parts. This is only ONE reason to NOT run your
engine in your garage for 'a few' minutes every so often during Winter storage!! If you store your bike in the Winter, or anytime
really, change the oil and filter and run the fresh stuff through the engine (cranking, no starting) before storage, and do not
start the engine until riding season. Use a good oil.  A cheap oil may NOT leave the parts coated with oil during long storage.

Synthetics: I used to do not believe the much greater cost of a 100% synthetic would pay for itself in anything but very cold
climates;...even considering the hype over longer change intervals.  However, even with oil prices in general going through the roof
things are relative, and synthetics are looking better and better for most everyone; this is especially so with the synthetic diesel
oils like Delo and Rotella. ...and good synthetic may well burn less, provide easier starting, and stay cleaner longer.  It may well
not cost too much more, over the long run.    

Does your synthetic oil have an additive to control seal swelling? Sort of a misnomer! Did you know that without that additive
in SOME types of synthetic oils, that your seals will likely SHRINK and leak? SOME seal treatment chemicals are lousy!...at
least on the airheads.   That does NOT mean that I am against full synthetic oils; my feelings about them has mellowed over the
years as they improved, and I know that ones like Spectro and even Rotella syn are quite good.    Another thing not known is
that some very old seal materials were not as compatible with modern synthetic oils.   The BMW Airhead main seal MIGHT have
been a case in point....and that seal was changed a number of times by BMW over the years.  The latest weirdo-looking Teflon-
like seal seems compatible with any type of oil.

Oils in general: Your oil must have the proper additives to neutralize the acids your engine produces from
gasoline and water from the air. Sulfur compounds (especially in petroleum oils) and water are hell on engine
bearings, which get eaten away, sludge forms, the corrosive products get burned up in the oil and tend to
form tough varnishes, cause sticky rings, etc. You may well see something in your owners book about oil
for your airhead, specifying SE oils. There were lots of problems with garbage SE oils produced by some
manufacturers. It was because of these borderline SE oils that SF came about. This was somewhat before
the engine manufacturers started specifying 'new' oils that supposedly had less friction.  BMW airheads
were designed for a GOOD SE oil, they LIKE SG oils. They might NOT be happy with anything past SG.
THE problem is that the SG rating gets mightily confused in advertising and how the cans/bottles are marked,
and, frankly, especially how marketed.  Here is something that is a bit subtle, that may have confused you
previously:   Many ""motorcycle-specific"" oils are sold as SG; or, are sold as 'meeting the quality
specifications of SK"...or somesuch words, perhaps the SK is SJ, or after SK.   These OILS are, however,
NOT REALLY LICENSED to REALLY be SJ, SH, SK, etc.  What they ARE is a lesser, SG perhaps,
containing ZDDP; which is fine and dandy for your airhead!...but would POISON car catalytic converters.
 These oils can NOT contain some additives, like ZDDP, and STILL meet the car and other specifications
for SJ, SH, SK, ETC....as ZDDP.  In a FEW instances, the oils are not 'energy saving' enough, and so on.  
It is a subtle point here that I am trying to get across.   If the oil is officially marked as a SJ, SH, SK, and
so on, and NOT SG, do not purchase it...it is for cars, NOT YOUR AIRHEAD.   If it has that wishy-washy
"meets quality standards of..." type of thing, it may well BE what you want if it is being sold very
specifically for motorcycles.  Read carefully.  If you have to, look at the manufacturer's website
information.....carefully. Dig, ask, you may learn something!

Techy stuff:

Viscosity index is a number that indicates the RATE of change of the thickness of something, within a given temperature range.
A HIGH index means the thickness varies LESS with temperature changes. ENGINE oils are specified at 210 degrees
Fahrenheit (98.9 C), except that engine oils rated W are specified at 0 F (-17.8C). This means that a 20W-50 is specified at TWO
temperatures, one for 20W (at O F) and one for 50 (at 210 F). If an oil does not have a W (at one time there were single weight oils
with W and multigrade without W) then it is not specified at O F. For the REALLY nerdy, SAE ratings are measured or specified
in centipoises at 0 F and centistokes at 210 F....and let's not get into Saybolt Universal! Converting between these is a
mathematical game.

CX oils have specifications for sulfur content, temperatures for release of various additives, etc.    CX oils are now up to and past
CF, and oils are quite common in the auto parts stores now that are rated SJ/CF (OR BEYOND). I even saw a container of Mobil 1,
a full synthetic, and all grades said SJ/SH/CF. Even that has been superceded now. The important thing about CX oils in general
is the protection for bearing corrosion and high temperature deposits that they were designed for, and THAT THE THERMAL
STABILITY OR BREAKDOWN POINT OF THE ZDDP TYPE ADDITIVE MUST MATCH THE OPERATING TEMPERATURE
OF THE ENGINE.  You will NOT find that information out easily.    NO ZDDP?....I don't really want one of those oils in my Airheads.
 I'd rather use a ZDDP-containing diesel oil.  Delo or Rotella anyone??
It was fairly critical years ago that CC oils not be used in diesels that ran hotter and needed CD oils. At one time, we had to watch
out for oils rated SE/CD, this was because those oils favored high temperatures of turbocharged diesels, and the additives did not
work well at lower temperatures of gasoline engines. Another interesting point is that diesel engines often run on very high sulfur
containing fuels. As you all know, some fuel and combustion byproducts get into the crankcase oil, contaminating it, so oils are
compounded to deal with the type of contamination expected.  If you get the idea here that good diesel oils DESIGNED for long-haul,
high mileage between oil changes, contain a big package to combat acids, yep, you are correct.  Both CX and SX oils have been
changed for many reasons over the years: antioxidants, pour point depressants, anti-foaming additives, anti-scuff additives,
detergents, slipperiness, other anti-wear additives, etc.   In general, diesel oils designed and sold for JUST diesels are much
better for an airhead engine than a SK car oil, and so on.   I recommend against the cheapest diesel oils....but the long haul truckers
type of oils...like Rotella...that is another story.  VERY good oils.

GEAR oils are specified for different temperature ranges than motor crankcase oils, this is particularly so with the W grades of
GEAR oils. Because of this, gear oils of maybe SAE 75 or 80 are similar in thickness to an engine oil of about SAE 40.    Use GL5
oils for your gearbox, driveshaft (if you have a wet type) and rear drive.  It is OK to use a wider range oil, but I'd rather see you
use a 75W-xx, than a 85W-xx.   There can be some good reasons, like hauling a trailer or sidecar with your AIRHEAD, that might make
a wider range ...up to 75 or 85 by 140 or 145 type oil nice for the rear drive, but I would NOT use it in a late BMW single sided drive
...particularly the BMW drives with the HOLE through the center of the rear drive (where an axle usually went).  This hole appears
only on very late model BMW bikes.

FORK OILS:

BMW red fork oil was basically a military Mil-5606 hydraulic oil, and those other branded fork oils are another subject entirely!
Basically you want an oil with a rather high viscosity index, perhaps over 300, as you don't want your suspension to act differently
as the temperature changes. Modern fork and suspension fluids are MUCH better than Mil-5606.   There can be a big
difference between one manufacturer's 3, 4, 5,  7-1/2, 10, or 15 wt oil, and another manufacturer. Fork oil viscosity ratings are
NOT government controlled!  If experimenting with oil grades, use the SAME manufacturer!.    Oil level in the forks should
be fairly equal (some later forks have UNequal amounts) and the proper amount.   Only a small increase in amount is useful in
SOME situations.   Don't use excessively heavy fork oils.   BMW has changed the amount of oil used in all their forks
several times over the years.   Oil quantity in some books may be either dry (just overhauled) or wet (drained to drip free).
If possible, try to get a fork oil that the manufacturer states has stiction minimizing additives. Oils that are marked
Suspension Oil and those marked Fork Oil, are often interchangeable in usage in our forks. Be careful not to get an
 oil that has too high a specification weight. Although the internal design of BMW forks has changed considerably
over the years, it is still true that going to or over 10 wt., except for those BMW specified for 10 ro 15, and except
for modified forks in racing, will give an uncomfortable, harsh, overly stiff ride, and you will not like the handling.
Thick fork oils are NOT a good substitute for sacked-out springs!

FRICTION:

Friction is a difficult subject, there are many types. Oil separates the potentially rubbing surfaces by very complex means.
Thick oils have more internal friction, but can support larger loads. An ideal oil would not change viscosity with temperature
changes. High pressure alone increases the viscosity of an oil [surprisingly], and this is why a thin oil can support heavy loads,
like in the rod bearings, but high viscosity increases fluid friction.

Please note: Speed of moving parts influences the heat developed, and high speeds mean faster shearing of oil itself, but
speed helps form a cushion in bearings, so higher speeds generally allow higher loading...that is ONE of the reasons why
lugging your engine is BAD.

SO, what should an owner of a BMW airhead do for oil? To my way of thinking, an owner should BEST use a quality oil,
designed for motorcycles, in 20W50 grade (unless you are riding in REALLY cold weather), and the compounding should
probably be part or full synthetic, and the zinc package should PROBABLY be at least 0.10%, but not over about ..17%, and
you will have to depend on the manufacturer's reputation in the matter of the quality of the base stocks and the zinc package, etc.

You wouldn't go far wrong in purchasing BMW oil from your BMW dealer, even though it was designed for the K models.  
You also will do well with Spectro part synthetic (Golden Spectro 4), Delo, Rotella...and some others.  Don't believe all the hype.

 I don't have any problems with those of you wanting to use synthetics in the transmission, driveshaft, and rear drive.

NOTE!!./....this article is not necessarily kept totally up-to-date.  See the author's website for a an up-to-date version.   http://bmwmotorcycletech.info
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