Oil filters, canisters, simplified

PLUS:  information on acceptable oils for the engine, transmission, driveshaft, rear drive; ...even fork oils....and
a short discussion on gasoline's AND OIL AND GAS ADDITIVES.

51-B
oilcansimple.htm

© Copyright, 2011, R. Fleischer

Be absolutely SURE that you read article 52-C.  It has information about engine oils that are becoming a problem for Airhead owners.  You will be vastly better informed.  I suggest you also read article 52-A.  It is almost mandatory for an Airhead owner to know the things in 52-A, B, C.

This article, BELOW,  glosses-over the detailed information in article 52-A....particularly about the oil canister and the so-called $2000 O-ring.

  The earliest Airheads, when not modified with a cooler, came with a three bolt outer plate, and an inner metal cap cover held to the canister center pipe by means of a single large bolt.  This system is just about foolproof.  Haynes is WRONG in NOT even illustrating this version!,,,,and wrongly labeling a later models sketch for the /5.  For the cooler models, the central pipe was changed, and the outer cover changed, and there is NO internal metal cap cover and single bolt.   After the early models with the internal metal cap cover with its single bolt, all models had an outer cover of one of several types, and all had the $2000 O-ring.

For ALL models EXCEPT those with the INternal single bolt cap cover, the following applies:

1.  BMW made some simplifications of the filters, after years and years of confusing folks.  NOTE that they still confuse some people. I am NOT surprised at that, and sometimes BMW forgets to package a part, or add extraneous parts in oil filter "kits"!  In addition, I have HEARD of an instance in which someone purchased a -575 cooler filter (not in a kit) and there was NO square O-ring in the box...so, beware!  BE SURE you understand what goes into YOUR bike.
2.   I recommend genuine BMW filters.   If you are in Europe, and can get quality filters, or can otherwise get the excellent Purolator's, that is fine too.  Fram filters are NOT on my acceptable list.   

BMW's hinged filters are BETTER than the one-length (one-piece) filters. Hinged filters are STRONGER, and FAR easier to install on some models!...in fact, the one-piece filters are near impossible to install on some bikes.   If you have a problem installing the hinged, two-piece filters, simply separate the two at the plastic strap.

3.   By now, almost all the REALLY OLD filters (hinged...and not..... with the confusing duplications of parts and numbers), are probably long since sold and gone.   Still, for reference purposes I have them listed.  On this website, the lengthy article 52-A, is there to inform you of every possible thing I know about ALL the oil filters, canister area, etc.  I DO recommend folks read it completely through, and follow the advice given.  It is not a how-to step by step article, nor simplified.  It was NEVER intended as such.
4.   NOTICE that Haynes and Clymer's, and BMW's OWN LITERATURE....are either wrong, or highly confusing!...in their sketches on the canister area.  BEWARE of their sketches!
5.   Those with the internal cap covers have a VERY simple, just about foolproof system....baring a sufficiently talented fool.
6.   The -570 filter is used for the NON-cooler later bikes.  With this filter, with its rubber at both ends, you do NOT use the medium size no longer available ROUND sectioned (-097  I think) O-ring, and also you do NOT use the medium sized SQUARE sectioned O-ring (-098  I think) that replaced that no longer available round one.   The -570 filter is hinged, and comes with a BONDED RUBBER tube at BOTH ENDS, and EITHER end can be inserted first.  The -570 is sometimes purchased by owners as part of a kit, the kit is 11-009-056-145.  USUALLY one does NOT use the paper gasket in that kit.  SEE website article 52-A for details on WHEN to use the paper gasket (which IS CRITICAL).  This -570 filter is SHORTER (both filter parts are shorter) than the next filter to be described, the -575.   Thus, the -570 filter, with its rubber ends, needs no other O-rings, EXCEPT the large white one...which is always the critical one, and which must ALWAYS be replaced.  The shim ALWAYS goes against the canister metal.
7.   The other filter is the -575.  It is hinged, LONGER than the -570, and this longer one is for cooler equipped bikes.   It has bonded rubber at ONE end, that end goes in first.  The outer end is not rubber bonded, and that is where the square-sectioned black rubber O-ring goes, it fits onto the groove for it on the outer cover.   The metal shim and white O-ring are the same situation as the first filter described, and same for yes or no using the paper gasket, as in article 52-A.  This kit is 11-009-056-146.   YES...ONE DIGIT away from the first one!  I have seen these kits come with one or two small coppery washers, I don't use them.
8.   Both kits SHOULD come with a single engine drain plug metal washer gasket.  20 foot pounds.

Information on acceptable engine oils:

    For some years, BMW has recommended NOT to use SJ and later oils.  Many will be sorry that they used such oils.  There is NO guarantee that SJ and later oils offer the full package of protection that BMW wants your engine to have.  Old Porsche boxer and VW beetle owners (as well as early Corvettes and other engines with flat tappets) have a similar set of problems.   You MIGHT get away with these oils...and you might be the unlucky one.  BMW's heat treatment of some parts has varied (they don't publish nor admit this), and for that reason alone, let alone other reasons, I agree with BMW in NOT USING THE WRONG OILS...although I don't go quite with what BMW said about ALL those acceptable grades:
BMW says to use SF, SG, or SH oils.  BMW says that these can have a suffix of CD or CE.   BMW also approves of CCMC-G4 or -G5 oils, and BMW says if the suffix of PD2 is on the container, that is also OK.      I believe BMW is correct for the SG.  I use Golden Spectro #4, in grade 20W50, year round, in my airheads; and it IS an SG oil.  I have vast experience with its qualities. 

Special note:   This is difficult to understand, so bear with me.   Many specialty oils, including Spectro's, have wording on the containers that you MUST take with a grain or two of salt (or, with understanding!).  If a manufacturer's oil does NOT have the SAE starburst seal and full approval RATING for SL or SM, ETC., then it is NOT REALLY such an oil PROVIDED that the oil IS a viscosity grade that is NOT a car grade...but there are some variances.   You might find the advertising or writing on the container saying something like this:  "Meets and exceeds the quality requirements of SL".  Be very sure you understand, that whether or not it says 'meets', or says 'exceeds', etc.....what it MEANS is that it is made to the QUALITY of the SL (or?) oil, but IS NOT ACTUALLY that grade NOR specification for that oil.   The API does not allow old oil grades like SG to be used nowadays FOR CARS.  SAE at the present time exempts (from certain of its specifications) 10W40 and 20W50 oils, and some others, as these viscosities are NOT specified for use in cars by the car makers.  There ARE certain oils that are not specific car grades, such as 20W50 and 15W50, and 10W40....that CAN have friction modifiers in them (Mobil 1 for instance)....and note that 05W30 and 10W30 ARE car oils...so THEY likely have very low ZDDP, IF ANY!!   Spectro does not make car oils.  Golden Spectro in grade 10W40 and 20W50 is a SG RATED and formulated oil, no matter what the container SEEMS to say about 'quality', or other weasel-words.  It is NOT RATED NOR APPROVED as SL, SM, etc., for CARS.  FURTHER, all Spectro engine oils generally contain 1800 ppm zinc and phosphorus.   See my VISCOSITY article for  a listing of some other oils with ZDDP, etc.     To make this a bit clearer, 10W40 and 20W50, 15W50, are NOT "car" oils.  THAT is how these oils can be sold with ZDDP in them.  These oils CAN be sold with friction modifiers, yet NOT marked with starburst symbol, etc.   Mobil 1 is like that.  

Perhaps Spectro and other motorcycle oil makers will straighten out what its containers say, and clarify their websites some day.  I think this is ALSO a matter for clarification by SAE and API.  Fat chance!   To its credit (because this is surely messy), at least Spectro DOES explain the seeming discrepancy...but ONLY on its website; and it is not the whole story.    The latest bulk jugs of GS4 20W50 oil I received do not even list anything but meeting the quality of SF/SG (and some Japanese specification numbers).

Some containers list SL, which it is NOT rated for, although its quality is exceptional.  Understand this mumbo-jumbo?  At the same time, some of the smaller containers of the same oil have had the previous markings.  Yes, all is confusing.   The easiest way to think about this is that this particular oil, Golden Spectro 4, in 20W50 (or, any Spectro engine oil) IS the one I personally approve of, it IS SG, and it contains the right amount (HIGH!) of ZDDP and other ingredients.   You can use the lighter grade, 10W40, if you insist on riding in weather below freezing.  

SG type or rated MOTORCYCLE SPECIFIC oils will likely have the correct needed amounts of zinc and phosphorus, etc.

Castrol's 4T oil, (and Grand Prix oil, which is the SAME OIL) in either grade 10W40 or 20W50, as appropriate to your climate, is SG rated and formulated.  Zinc component is 1100ppm; Calcium component is 1900 ppm; and Phosphorus component is 1000 ppm. 

The following is an edited (for clarity, typos, and removal of bad hyperlinks, etc.) version of what was posted on the Airheads LIST on 07/11/2008, as there was an extensive thread about these oil ratings, etc.   Notice how my information, above, from long ago, is so accurate (my ego runneth over!). Consider that OAK is MY personal Airhead guru!  ::

Snowbum's comments:
If YOU want to use REAL, RATED, LICENSED, SJ or later rated oils in your Airhead engine, that is your choice, and I hope you have REAL reasons to do so, rather than advertising hype.  I have 'no problem' with you using the cheapest oils, such as SJ (or later symbol) car oils...it is YOUR bike, and the engines can be rebuilt, if expensively. Some have had good results over considerable mileage's with these car oils in the distant PAST.  If you have a leak, camshaft lobe or followers wear, or other problems, it is not MY problem, it is YOUR problem.   It is MY BELIEF that some BMW parts are variable in factory heat treatment, which MAY account for large seeming discrepancies in service life of things like camshafts and followers, as some do get good life with cheaper oils.  BMW also uses cam profiles and followers that are, essentially, similar to a rotating flat tappet engine.  It is THOSE older engines, like in the sixties muscle cars, and some Porsche's, that are adversely affected by modern "car" oils.    I simply will NOT take the chance.   That is why I insist on a quality motorcycle type such as Golden Spectro or specific versions of Mobil 1 or one of the diesel oils NAMED in this article for my Airheads and my K bike too (the K bike is vastly less susceptible to problems). I simply don't want to take the chance on no or way too little ZDDP when my engine decides it needs it....AND, I want an oil with other good properties.  Good properties include the oil sticking to the surfaces for long periods of inactivity; good corrosion resistance; good thin film performance, LOW boil-off (some oils boil off the first part quart very quickly...they are high volatility....); and other characteristics.   I really want the oils to hold up.

 A good oil really does cut down on wear, and in some instances is THE difference between lots of wear in extreme conditions (VERY hot engine, or very cold starting, etc....).

I don't use FULL synthetics in my airheads, but have no objection to Spectro's, in YOUR airhead.  There ARE good motorcycle oils from Redline, Motul, etc.  I also have no objection (BUT SEE BELOW!!) to your using CERTAIN types of diesel engine oils:  Rotella, Delo, and Delvac.   

If you ride in really cold Winter weather, well below freezing, you can consider a lighter grade, perhaps a 15W50, or a 10W40.  Your owner's manual has the grades suggested, although that is probably not in-date for what is available in modern oils.

Be advised that diesel oils of the bulk type mentioned above WILL be having much less ZDDP put in them, and this started in a small way in 2007.  Some type of slow phasing out or a reduction was mentioned in a number of places; due to some diesel-equipped cars and trucks that are having catalytic converters installed.  Diesel oils need more detergents and dispersants in them.   HIGH levels of detergents are not necessarily the best for Airhead engines.
 

Besides the heat treatment variability of some BMW parts like camshafts and followers, which influence my recommendations...., ZDDP type additives TEND to come into their own (they do offer some help earlier) at the point that things are getting a bit extreme....very high rpm, very hot temperatures, lengthy riding at high power levels....etc.   ZDDP is fairly critical when breaking in a new engine, or even just new rings or cam followers. 

Some additives work at very cold temperatures for cold start protection.  Most are not too good at this....and most not good at all if the engine sat for a few months.   Many cheaper oils are just not good at keeping an oil film on parts if the engine sits for some time.  The proper additives of good quality will help here...another reason to purchase a quality motorcycle specific oil.

ZDDP protection tends to come into play at cams, lifters/followers/cylinder bores, perhaps piston rings.  Once there is enough of the compound in the oil, you get no more protection, only cylinder deposits from more.  0.15% is probably just fine for very full protection.   0.2% is likely too much and under .11%  too little.  I get into this deeply in my Oil Essay article.  I selected Golden Spectro 4 in 20W50 as my primary airhead engine oil, as it has never shown the slightest problem with cams, followers, etc., and the additives do NOT burn off quickly like cheap oil does, and it DOES have many other desirable qualities.   Oak likes that oil, I like that oil, every test seems to show it is a truly good oil.    I don't intend to get into a lengthy argument on oils.  Been there....done that.     I have nothing against you using the full synthetic version of the Spectro oils either...pretty good stuff!  Do change it regularly, don't try to get 12,000+ miles on it (unless on one long tour!); some of the additives will have burned off or converted or otherwise become ineffective...if there are enough start cycles ...and miles.

A 20W50 oil is almost always better, from the same manufacturer, than a 10W40.  The wider the range (divide the second number by the first) the worse the oil will be, long term (as miles accumulate).    You can get away with a wider range with a full synthetic, the 15W50 FULL synthetics are generally good.   Castrol GTX in 20W50 is NOT a great oil for Airheads, no matter the hype.  I no longer trust Castrol oils....since the lawsuit.  It is DIFFICULT to find out what the ZDDP level, if any, is in Castrol oils these days, and their 'full or partial synthetic' oils may not have ANY synthetics in them (I am NOT kidding, that was the thing in the lawsuit that an unsophisticated judge ruled on).  NOTE, however:  Castrol's 4T oil, (and Grand Prix oil, which is the SAME OIL) in either grade 10W40 or 20W50, as appropriate to your climate, is SG rated and formulated.  Zinc component is 1100ppm; Calcium component is 1900 ppm; and Phosphorus component is 1000 ppm. 

As oils get miles on them, the bigger molecules are sheared by various engine forces and the oil is no longer the viscosity you had when the oil was fresh.   That does NOT mean that you should use single weight oil!  

Another problem is that  ZDDP is actually used up and no longer has the necessary levels in SOME oils containing it.....after maybe 4000 miles, in some cases less.

With reasonable usage, and not too many short trips under 10 miles or so, you can probably change oil at 4000 to 5000 mile intervals, and the filter every second oil change.  You can go farther with full synthetics in general, although the ZDDP tends to decrease, perhaps too much of a decrease.  I personally have NO problem with going to 6-8000 miles on Golden Spectro 4, which is a PART synthetic oil......on a long trip.

NOTE!    see:  http://motorcycleinfo.calsci.com/Oils1.html
That is a hyperlink to a LONG article by a layman, on oils.    I disagree with a FEW things in this article, but the VAST majority I DO agree with.   So, if you are REALLY interested in information on the always-controversial information on oils for cars, trucks, bikes, diesels, and whatever....the article has a tremendous amount of information. AGAIN, I disagree with a few things in it, and I disagree with a few conclusions.   But, all-in-all, this is THE BEST article I personally know of (outside of my own!) dealing with oils.   I suggest you read it.  These articles, points towards sales, but nevertheless is quite decent in most respects, for the zddPLUS products.

Miscl.:  Additives, more on engine oils, some vastly more nerdy technical things, Gasoline's, ETC.    

There are hundreds of additives that one can purchase to doctor up one's ENGINE oil. Please do NOT purchase and use ANY of them.  However....some are GOOD for your GASOLINE now and then   The use of Standard/Chevron's Techron additive (cheaper and better overall to get it by purchasing the gasoline, I've done the math for you, assuming you start with a modestly decent combustion chamber) is a good idea.   NOTE:   Techron additive is actually a polybutane amine compound. There is a boron component, I think.   Originally identified as F310, it was reformulated many times, and in 1980 it became a polyether amine, and so remains today, with minor changes in overall formulations.     FYI, for modestly coked up combustion chamber/heads, use of bottled Techron as found at your auto-parts store, and FOLLOWING THE INSTRUCTIONS, gives a mixture that is about TEN times the strength of the Techron in Chevron Gasoline's at the pump.  You CAN use this bottled stuff a couple times a year, and it WILL keep your combustion chambers far cleaner, and it DOES help clean them if already carboned up.   Use of the Techron containing pump gasoline WILL help keep your combustion chamber cleaner.  Once cleaned, it is probably cheaper to purchase the Techron, for overall effect, at the pump, in the gasoline.   The bottled formula is not just concentrated, but is a slightly different overall formulation, to work faster.    As a bit more background, California was the leader in the U.S. to require various formulations of gasoline's to reduce smog.  The California Air Resources Board (CARB) REQUIRES deposit control additives, this was set in stone in 1992, and modified in June of 1999 for even more additive levels.  Intake valve deposits are under a certified testing routine, ASTM-D-5500 for all gasoline.    Techron works better than other additives, near as I can tell, and the bottled additive, used to help clean already coked engines, contains light aromatic naptha, stoddard solvent, benzene's, xylene, cumene, all are besides the main working ingredient.  Another thing about gasoline's:   So-called "Tier-1" gasoline's ARE better.  Do a Google search and read up on them.

Additives are hyped.  People do NOT want to face up to the FACT that THEY are influenced by advertising.   People WANT to feel like they are effective in life, have done something good, have an inner need.  Don't bother with most additives.  They are a waste of money, and in some instances can do damage to an airhead.  Techron for gasoline is an exception.

BMW camshafts and followers are very conservatively designed and built, with long life, quietness of action, etc., as goals.  The cam lobes are mild in rate of lift rise.  Still, heat treatment appears variable, and that is why I recommend NOT using cheap, or even expensive, "car" oils.   Besides this, BMW cam and followers are mechanically such that a good oil film with ZDDP is almost an absolute necessity at that point.

SOME oils are NOT good if the engine is run INfrequently.   Some oils will NOT hold up to the very hot temperatures in the Airhead valve areas.  Just because the crankcase oil measures 225°F perhaps, does NOT mean the oil is that temperature at the valve guides.    Some oils will drip off parts until the parts rust.  In particular, this is a trait of single weight motor oils.   There have been instances of moderately frozen-up engines from sitting with car oils in them.

Oil changes need to be done more often in high power high temperature riding.    For short, say under 10 miles commuting trips, also change the oil more often.    Filters generally are OK for two, sometimes three, oil changes...perhaps even up to 9000 miles, or more, in a reasonable length of TIME.  That does not mean I approve of 12000 miles between filter changes, except under very specific situations.

Airhead engine tolerances were NOT designed for use with 5W30 oils, nor do they do very well on many 10W30 or 10W40 or straight weight oils.    Use of such car oils should be restricted to very cold Winter conditions ONLY, and even then I do NOT like them used in Airheads...I'd MUCH prefer you used, for severely cold weather, a full synthetic, such as Mobil 1, that has lots of ZDDP in it...so select the correct version and grade!

 I suspect that the Airhead rear drives may not like the new wider range hypoid oils that are available, such as 75W140, but have no proof, and yet I think those oils might be better in our Airheads for very extreme situations, such as pulling a trailer or sidecar, or VERY hot weather at speed.  I may have more to say on this in the future.

I am very suspicious of some magazine reports on oils testing.  They do not test for actual long term engine wear; nor usually for usage (some cheaper oils are burned off much faster, particularly initially).  Reports from a lab on metals wear as seen when analyzing oils, is NOT enough information.

I don't trust some synthetics for maintaining seals size and condition.  PART synthetics, like Golden Spectro 20W50 (which I trust, having years of experience with it, including engine teardowns), are very good. 

I will ADMIT:  Full synthetics with lots of ZDDP seem to be the better choice for more severe conditions.  Some of the better full synthetics are quite good these days at all temperatures and conditions; so I have reduced my previous cautions about them.

Some manufacturer's change formulations without telling anyone.  This is QUITE common.  Castrol GTX changed.  Castrol won a lawsuit, dealing in what the word 'synthetic' really means.  BEWARE of Castrol engine oils!....... except 4T.

For touring use, with longer mileage between engine starts and stops, in mild to moderate conditions, 5000 miles between oil changes is very reasonable.  On one long trip, over some weeks, I would not object to even a longer drain interval, if using a quality oil.  With a full synthetic, and long trips, rather long drain intervals are probably OK.  Just do not go overboard here....remember, you want the ZDDP and other oil additives to be in YOUR oil, not burned off or simply contaminated from the high mileage.

Slick 50 is dangerous to your engine's health.  It is TRUE that some types of additives will give less friction, and maybe a small bit of  higher fuel mileage.  That does NOT mean less wear!!!

Some additive products will clump out, plug oil passageways.  

Bardahl, Rislone, Marvel Mystery Oil....all are ugggh for airheads.  In a few rare instances, Marvel is used for upper end cleaning.  This is particularly so on K bikes, with the notorious starter sprag clutch, where Rislone also sometimes does help.  Keep in mind what I said earlier herein.....very HIGH detergent levels are NOT good for your Airhead engine.

I have actually gotten into the technical area of oils to a great depth.  Jigs, test engines, additive types, temperature effects on residues, neutralization number, channeling, shear strength, film strength, foaming, detergency, oxidation....etc.....

The only area I could never get 100% agreement on, with engineers, is seal compatibilities....due to all the variables.

Ashland Oil Company makes Valvoline brand products.  Valvoline 4-stroke motorcycle oil in 10W40 (COLD climates) or 20W50 for moderate climates, is still a good oil for Airheads.   The zinc content of these two oils is 0.112%, phosphorus is 0.103%, calcium is 0.182%, and sodium is 0.052%.

For Shell Rotella-T, in 15W40, the calcium is 0.27%; zinc is 0.135%, and phosphorus is 0.120%.

Do NOT use single grade oils in your BMW airhead unless you have a VERY good reason....such as being someplace in the world you cannot find a multigrade oil.    In almost every respect, modern multigrade oils are vastly better than single grade oils, especially in NON-car viscosity grades.

For JUST fresh rings or bore job or both, break-in is probably better on a non-detergent single grade oil, but with the type of break-in I recommend (see my article), only full synthetics should be totally avoided during break-in of fresh rings.  

Most engine wear is in the first minute or so of cold weather startup.

Changing the oil regularly is THE most important thing.  That does not necessarily mean every 1000 miles (unless you put on 100 miles a month) ...and it might be 5000 or 6000 or longer.  Depends on conditions and usage.

Do NOT run your engine every month or so for a few minutes in your garage during Winter storage.  This will result in moisture condensation in the oil, and perhaps sulfur-based acids.

A transmission and rear drive oil additive ...do not use with synthetic oils is Dow Corning M Gear Oil Additive. Comes in quart containers. Shake well and use ONLY the concentration I recommend ...and absolutely not the 5-10% Dow suggests on the container.  So, I say, use 18 to 20 cc  for your transmission that contains 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.   It may increase the lifetime for the bearings, etc.   ABSOLUTELY do NOT use this product with synthetics, and DO NOT increase the dose!    For the rear drive, you can use about 2% or so.

MORE on Engine oils; more nerdy stuff:

SE oils, way back when, were specified by BMW.   SE oils were not, however, held to tight enough tolerances by manufacturer's....there were real abuses, and SF replaced SE.  

BMW airheads prefer a GOOD quality SG oil.

'Viscosity index' is a number that indicates the RATE of change of the thickness of the oil, within a given temperature range.  A HIGH index number means the thickness varies LESS with temperature changes.  ENGINE oils (as opposed to GEAR oils for instance, but are lots of different types) are specified, generally, at 210°F (98.9°C), except that engine oils with a "W" are specified at 0°F (-17.8°C).  This means that a 20W50 oil is specified at TWO temperatures; for 20W at 0°F, and for 50 at 210°F.   For the really nerdy, SAE ratings are measured or specified in centipoises at 0°F and centistokes at 210°F.....and, let us not get into Saybolt Universal!!!  What 20W50 is SUPPOSED to mean, and generally DOES mean, is that at 0°F, a very wintery temperature, that oil should be the same thickness (viscosity) as a UNcompounded (single weight) oil that would be called SAE 20 is at that cold temperature.    The "50" means that at 210°F, that oil should be as thick as a SAE 50, AT that temperature.

Cx oils (replace the x with the latest letter) have specifications for sulfur content, and for temperature for release of various activity of additives, etc.  Cx oil rating is concerned with many factors, some of which are pertinent to airhead engines, some are not.  A problem with Cx oils is the FACT that most of the active agents for protection of metal to metal contact are for vastly higher temperatures (after all, they ARE diesel engines) than in airheads.  Thermal stability and breakdown point of additives are different.  It was fairly critical, many years ago, that Cc oils NOT be used in diesels that needed Cd oil.   We had oils, most are like this today, that are rated for gasoline engines and diesel engines, and you will see the rating as, perhaps SE/CD, etc.  These crossover oils, when sold for cars, tend to NOT WELL favor the high temperatures of the turbocharged diesels, and the additives, or some of them, do NOT work well at gasoline engine temperatures.  Sx oils have changed over the years, and the additives and compounding is quite different from earlier oils.  Many characteristics are for increasing fuel mileage and decreasing damage to catalytic converters, and in some instances to help with decreased clearances in very modern engines.  All sorts of considerations are made, antioxidants, pour point depressants, anti-foaming, anti-scuff, detergency, slipperiness, etc.   There ARE some diesel oils that are USED TO BE fine in Airheads, such as Rotella and Delo and Delvac.  These oils, at least through 2006, had quite adequate amounts of ZDDP, which car oils after SG did not.  MOTORCYCLE oils in 20W50 and 10W40 do not have to eliminate ZDDP,..... those grades are EXEMPT from the SAE and API requirements, and thus they can be REAL SG oils...and can state on the container that they meet the quality (not specifications) of SL or anything else.  Shell Rotella-T in grade 15W40 is still OK in airheads at the time I updated this section.

Gear oils are specified for different temperature ranges, and their additives are most active in those temperature ranges.  This is particularly so with the W rated gear oils.  Do NOT think that a 80 weight gear oil is as thick as a 80 weight engine oil might be at the same temperature;....NOT SO!

BMW fork oil, the old original red oil, was a military specified hydraulic oil, actually the mil-spec was MIL-5606.  Quality fork oils available today are better, especially for viscosity index (nice to have those forks handle the same after a few miles of bumpy road) and anti-stiction qualities (nice to have the forks, if properly aligned, to not act like solid steel ...no suspension....over tiny irregularities in the road surface).  Generally, BMW has manufactured the various hole sizes, etc., inside the forks, for use with a rather thin oil, roughly SAE 4.  In another measuring system, it would be about a SAE 7.    Use of oils of 7.5 is fairly common, but 10 and up usually means something is wrong except on the R100GS, etc., with 10 in one fork, 15 in the other, per spec.    Some oils that are OK for use in BMW forks may be marked as Suspension Fluid...OR...fork oil.     The proper and exact viscosity for the fork oil in all but the R80R, R100R, R80GS, R100GS, is SAE 4.....but to be more exact, the viscosity should be 13.2+- at 40°C (104°F).  You need to know the viscosity at that temperature area, and can mostly forget the other temperatures that are often quoted.   One manufacturer's SAE 5, or any other fork oil, is not the same as another's!....so see their specification sheets.    When trying different fork oils, use the SAME manufacturer.  There is more on fork oils a bit further down in this article.....AND...I have an article, viscosity.htm, that gets DEEPLY into fork oils (and some on engine oils), naming the brands and models and viscosities, etc.

Friction considerations:
Friction is a difficult, many-types consideration.  Oil separates potentially rubbing surfaces by very complex means.  Thick oils have more INternal friction, but can support heavier loads.  An ideal oil would not change viscosity with temperature change.   High pressure ALONE INcreases viscosity of an oil....this is why a THIN oil can support heavy loads, like in the rod bearings.    A thin oil is far better for COLD STARTUP.  Because of these things, use of thick oils is not a good idea in BMW airhead engines.  It is just ONE reason, of many (including generally being poorer at sticking to surfaces during storage), that single-weight oils are NOT a good idea, at least nowadays, when the multigrade oil performance is vastly better than 50 years ago.  I can see almost no use for single grade oils, except maybe for first 50 miles of break-in. 

If quality multigrade oil was not available in the very hot deserts of the Middle East, a single grade, perhaps 40 wt., would be OK.

Speed of moving parts influences the heat developed, and high speeds of those parts means faster shearing of the oil itself, but, conversely, speed helps form a cushion in bearings (of many types), so higher speeds generally allow higher loading (in general speed here means rpm).  That is why lugging your engine by using lots of throttle at low rpm is not a good idea.     BTW.....after the oil warms up, and you are at idle rpm, there is very little oil coming out of the pressure relief valve area, to lubricate the chain and sprockets,.... so lengthy idling....and especially too low an idle rpm...is NOT a good idea.  This is in addition to the bearings in the engine not having enough pressure with lengthy idling, to support the oil film at low rpm....especially on a well-worn engine.

Transmission and driveshaft oils:

Snowbum (that's ME!) uses 80W90 GL5 oil at the transmission and driveshaft (on models requiring oil in the driveshaft) and rear drive.  80W140 or 85W140, etc., in GL5 type is also OK, although I have mixed feelings about them.  I would consider using them if you live in the very hottest climates or pull a trailer or sidecar.   

Disregard information you may have heard about sulfurs in GL5 being bad on airhead rear drive brass or bronze parts.   Is NOT TRUE.

MORE on Fork oils:

  I prefer Spectro's fork oils, or suspension fluids.  They are GOOD, have low stiction, wide temperature range (decent VI too), and the viscosities can be depended upon.   NOTE that back in the early Airhead days, the BMW fork oil was red, and was really a military hydraulic oil, you could find its full specifications using a search engine for:  MIL-H-5606E.  Just to save you the trouble, the viscosity specifications for that oil are:
MINimum 4.9 Cst at 100° C
MINimum 13.2 Cst at 40° C
Maximum 600 Cst at -40° C

Due to how it is specified, and the lack of superior stiction fighters, and some other characteristics, you are MUCH better off with a REAL fork oil....especially a full synthetic fork oil.    For the various fork oils and suspension fluids, the various manufacturer's do not agree on measuring viscosity.  That is nearly cut and dried for engine and gear oils, not so for these oils.  Because of that, stick with ONE manufacturer if playing with viscosity grades.   Except for some GS models, all the old BMW's needed a very thin oil, roughly SAE 4.    For the most part, you can translate that to modern 5 to 7-1/2 fork oils.     Note the 4.9 and 13.2 at the temperatures cited; compare those figures with YOUR manufacturer's figures.   A formula to convert Cst to SUS is in the viscosity article, link just below.  But, HEED my remarks about sticking with ONE manufacturer.

****NOTE!!  On this website is an article on oil viscosities, and other characteristics, by brand, etc.  Lots of information on shock and suspension fluids/oils and some on engine and gear oils too.    VISCOSITY.HTM

revisions:
01/16/2008:   revised to include latest information on oils, and to clarify details on canisters, etc.
01/22/2008:  updated for clarity only
07/12/2008:  revised item 2, add more information on oils.  Oak's comments added. Entire article edited a bit.
07/14/2008:  revise the article in line with latest reports on diesel oils.
04/13/2010:  slight updating, adding some oil characteristics content; + adding a hyperlink to my viscosity article.
04/24/2010:  Go through entire article and fix typos, and bring up-to-date. A tad more on 11/12/2010.
11/18/2010:  Add Castrol 4T zinc amount
02/24/2011:  was 52B

© Copyright, 2011, R. Fleischer

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