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How to understand Motorcycle Oils...
And How to Choose Motorcycle Motor Oils...

Oil: Basic Theory 1101 -- friction & how oil works...
Oil: Intermediate Theory 2230 -- formulation, viscosity, ratings, dino vs. synth...
Oil: Advanced Theory 3150 -- what breaks it down, good & bad additives...
Oil: What You Really Need To Know! -- the short version.

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Oil: Basic Theory 1101

   In any situation where two surfaces slide over each other at medium to high speeds, the rubbing of the two surfaces against each other creates friction. Friction translates into vibration as one surface bounces off the other repeated, and this bouncing causes both wear and heat (since heat is nothing more than vibration at an atomic level).

Friction In the Simplest Terms
   Think of an "Indian Burn" from 3rd grade (no slight meant to our native tribes) -- this is an example of friction caused by two surfaces (skin on skin) in motion relative to each other. It burns (causes heat) and it wears away a thin layer of skin.

   The simplest way to reduce friction is to use a material which is designed to dampen the vibration, while at the same time being slippery enough to reduce the interaction of the surfaces, by doing two things: filling up the voids between the parts (including any microscopic bumps and pits), and being able to roll or slide over itself, so the two main surfaces never actually meet (at least in an ideal world). Many fluids and powders can fulfill this requirement in general, from graphite powder to mineral oils, from molypolydisulfide (anti-seize) to automotive grease.

   A gasoline-powered engine (such as in cars and trucks) has surfaces that are in very close quarters (tight tolerances) and which are moving incredibly fast compared to each other. Plus, the frictional surfaces and any lubricant used on them are subjected to a wide range of heat (from below freezing in some climates before the engine starts, to well over 2000°F along the walls of the cylinder during detonation for a poorly tuned engine). The lubricant is also exposed to a variety of chemical contaminants (including sulfuric acids, carbon molecules, gasoline vapors, et cetera). The only obvious answer which is cost-effective for this particular in-engine environment is motor oil, and many different types of motor oil exist to fill that need.

Motorcycles Engines are Special
   In most motorcycle engines, those same engine surfaces generally move much faster than they do in car and truck engines, conventionally twice to ten times as fast, due to difference in RPM ranges, stroke lengths, stroke speeds (i.e. - piston speed), et cetera. Additionally, most modern street-oriented motorcycles have a "wet clutch", which means that the clutch plates also sit in the same oil that the rest of the engine uses to lubricate itself. Most also have the transmission also sharing this same oil. Throw in the fact that some motorcycles are still oil-air cooled (which causes the oil to run 1.5 to 3 times hotter than a water-cooled engine). These four differences (speed, clutch exposure, transmission exposure and oil temp) are the grounds for the basic differences between formulations of motorcycle oils and car oils.
I.E. - Mobil 1 V-Twin 20W-50 contains 25% more anti-wear and anti-oxidation additives than the equivalent traditional Mobil 1 automobile oil.


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Oil: Intermediate Theory 2230

   Every manufacturer which makes motor oil (whatever the intended use), controls the manufacturing process to ensure that their product comes out with certain qualities, from a specific weight range, to specific viscosity and additives (both discussed further down). This process of creating a specific blend is called formulation. As far as I am concerned, for purposes of this discussion, we can ignore the actual steps used in refining crude oil and formulating basic motor oil, but if you're interested in more information about the mechanical process, you can visit
How Oil Refining Works.

   All motor oils are graded by viscosity, which refers to how well the oil flows at specific temperatures (at 40°C, and at 100°C, are the standard measuring temperatures). The higher the viscosity number, the thicker the oil, and the more slowly it will flow through a specific sized opening. Generally, the higher the viscosity (also called "weight"), the thicker the oil is, and thus the better the oil is at reducing friction when the oil is hot.

MULTI-WEIGHT (multi-viscosity) OILS:
   A multi-weight oil is an oil formulation that acts as if it has two different viscosities, depending on the temperature. At the lower test temperature (40°C), it flows as the first number would indicate, and at the higher test temperature (100°C), it flows as the second number would indicate. This multi-weight nature is made possible by the addition of long-chain polymers to the oil, which are coiled up when cold, but straighten out when hot, and thus change the flow characteristics of the oil. Thus a 10w40 oil will flow like a 10 weight oil when at 40°C (fairly thin), but will not thin out more than a 40 weight oil would when hot (100°C). As a second example, a 10w60 oil will flow like a 10 weight oil when at 40°C (fairly thin), but will not thin out more than a 60 weight oil would when at 100°C -- and most motorcycle engines can't take a 60 weight oil (even if it will thin out again as it gets even hotter) without starving the tighter passages for oil supply!

Engine Manufacturer's Oil Specifications
   The thicker the oil, the more it will dampen vibration, but at the same time, an oil can be too thick (especially when cold) or too thin (especially when hot) for the pumping system of an engine to move it effectively. Oils that are too thick (or contain too long a polymer string, such as a 10W60) can also starve tight passages, such as between the piston rings and cylinder walls, of adequet oil supply (not enough of the thicker molecules fit in the same space). Thus engine manufacturers specify a recommended weight class of oil for use in their engines, one which balances the need for friction reduction with the oil pump's ability to move the motor oil when the oil is cold and when the oil is hot, and which will reach all parts of the engine properly at all times. Since motor oil normally never gets colder than the ambient environment around the engine, engine manufacturers often specify different weights or viscosities for motor oil for their engines based on the ambient temperature the engine is to be operating and parked in.

   Some manufacturer's are touting their oils as being clinging or magentically binding oils which cause a film of oil to stick to metal parts even when the engine is switched off (to provide protection on start-up). Virtually all motorcycle-specific oils have some degree cling action (haven't found any that don't), and this is a polar-attraction feature of specific base stocks (PAO Group II thru IV). Don't sweat it -- all good motorcycle oils that meet your bike manufacturer's specs will have about the same degree of cling to them irrelevant of brand, since they are all generally made from one or more the same three types of base stocks, and the cling or magnetic message is just a way of marketing a feature that has always been there.

   Manufacturers have traditionally refined conventional crude oil into various products, including motor oil. This process, if not amended further, results in what is often referred to as "Dino Oil" (dinosaur oil, although that's a misnomer, as oil is actually created of decomposed plant materials, mostly single-cell plants). Dino oil contains some degree of impurities (most are filtered out), as well as varying lengths of the hydrocarbons the make up the actual oil, including (unfortunately) paraffin waxes.
   Synthetic for our purposes here means "not occurring in nature." Synthetic motor oils are traditionally made by further processing the base dino oil to extract all the hydrocarbons of a specific length, and using that extraction as the "synthetic oil". Sometimes chemical or electro-mechanical coaxing the incorrect-length hydrocarbons to split and/or combine to form the desired length hydrocarbon is also done prior to the hydrocarbon selection and separation. This generally separates out the impurities in the process, since the base stock remains behind and only the desired portion is removed to be used. Thus, a fully synthetic oil is one which is uniform in it's composition (at least prior to addition of additives, et cetera). The benefit of having an uniform base is that every molecule will act as it should, providing the desired lubrication.
   It is also possible to build the hydrocarbons for a full synthetic oil from scratch in the lab, basically manufacturing hydrocarbons of the required length. Obviously, synthesized hydrocarbons would be inherently pure (free of impurities), including paraffin waxes. As far as we are concerned, as long as the results are identical (uniform hydrocarbon length, free of impurities, and non-existant parrafin content), either manufacturing method is equally desirable. The question then remains to the actual manufacturer of whether it is more cost-effective to remove the impurities and coax and separate the desired length hydrocarbons out or to build them from scratch. Either way, they're not likely to tell you on the bottle, so you'll probably never know before use (sometimes you can tell post-use by the presence of sludge, indicating paraffin content in the oil, which in turn means it was a dino-synthetic and not a lab-synthetic).
   Synthetic-basis (aka mixed) motor oils are a combination of the two differing types (dino oil and synthetic oil), which are created for cost-effective purposes. Such mixes provide much of the benefit of a synthetic while off-setting the cost of creating a full synthetic.

Do Synthetic oils cause leaks in old engines?
   Most synthetics contain high detergent loads and little or no paraffin content. The combination can cause existing paraffin sludge deposits to be washed away, exposing damaged seals that were previously sealed up by the presence of the sludge. Thus, while the synthetic doesn't create the leak, it appears to, since the leak starts weeping or leaking shortly after switching to a synthetic. The reality is that the leak was there all the time, and poor oil maintenance was responsible (the seals, once blocked off, deteriorate because there is no fresh oil running against them). Note that switching back to a dino-oil won't fix the leak...
   However, the break-down and removal of sludge in the engine is far better for the engine's lubrication and cooling, so it's a switch I recommend. If you pop a leak, the leaking gasket was toast already anyway and needed to be replaced -- so replace it.

Are all Synthetics Equal?
   Unfortunately, a synthetic-basis mixed motor oil can be labelled as a "synthetic motor oil" under US trade law and resultant court decisions, which means it can be hard without reading the label exactly and doing some research to know whether an oil is truly a full synthetic or a partial-synthetic mixed with dino oil. This isn't the case in Europe, where the synthetic label can only be applied to oils created by lab creation of pure hydrocarbon chains. But oils formulated for the European market normally use different formulations that US-market oils (example: Castrol GPS, which varies formulations between the US, Europe and Australia).

   The American Petroleum Institute provides standards for rating the viscosity and certain contents of motor oils. This permits oils from different manufacturers to be compared in terms of standard viscosity weights. It also permits oils from different manufacturers to be compared in terms of meeting specific guidelines for content formulation (primarily to ensure compatibility with specific pollution control systems mandated by the government, such as catalytic converters, as well as fuel-mileage increases by reduced oil-based frictional loses), but it refers specifically to automobile engines, not motorcycle engines.

Is SL or SM better than SF/SG for my Motorcycle?
   API's Standards Rating is influenced by government mandates (such as pollution control), and thus oils meeting newer ratings do not necessarily perform better (or even the same as) oils meeting an older rating, depending on your motorcycle engine type. API standards are created for automobile engines, not motorcycle engines. For their rating system explained, see the API MOTOR OIL GUIDE (current guide with SM classification on it).

  • SA through SE   OBSOLETE -- Use SF/SG or SH unless you find motorcycle oil which still meets the original rating that your bike calls for in the owner's manual. I am not familiar with any SA/SB/SC/SD/SE rated oils still on the market, but there may be some available for special vintage class bikes (bikes built between 1910 and 1970).
  • SF & SG   TECHNICALLY OBSOLETE FOR CARS, BUT STILL IN COMMON USE FOR MOTORCYCLE OILS -- You can find motorcycle oil which still meets the SF/SG rating (such as offerings from Castrol, Mobil, Royal Purple, Amsoil, Bellray, Motorex, Motul, Repsoil, etc). If your bike calls for that in the owner's manual, there are still a large number of motorcycle-specific motor oils on the market that are SF/SG rated, including every motorcycle oil which meets the full JASO-MA specification. Most current motorcycle engines still call for SF/SG rated motor oils. If you can not find an SF/SG rated oil and that is the rating called for, use an SH or SH+SJ rated oil -- but do not use API SJ, SL or SM!
  • SH   Technically obsolete.  This oil specification is used by some motorcycle manufacturers, and you can still find many SH rated motorcycle oils on the market. Do not use if your motorcycle calls for API SJ/SL/SM rated oils (only a few do).
  • SJ   Technically obsolete.  For 2001 and older automobile engines. An "Energy Conserving" motor oil (something good for late model cars, not most motorcycles). Note that this standard reduces the phosphorus contents of the motor oil, which is not necessarily a desirable reduction for most motorcycle engines. Check your motorcycle owner's manual specifically for recommendation of an SJ-rated motor oil before using it in your motorcycle, or stick to using SF/SG-rated, SH-rated or dual-rated (SH+SJ) motorcycle oils instead. Do not use unless an API SJ rating is specifically called for by your motorcycle manufacturer.
  • SL   Technically obsolete.  For 6/2001 - 11/2004 automobile engines. An "Energy Conserving" motor oil (something good for late model cars, not most motorcycles). Note that this standard reduces the ZDDP (zinc and phosphorus) additive contents of the motor oil even further than SJ rated motor oils, which is not a desirable reduction for most motorcycle engines. Check your motorcycle owner's manual specifically for recommendation of an SJ or SL rated motor oil before using an API SL rated oil in your motorcycle! Do not use unless an API SJ or API SL rating is specifically called for by your motorcycle manufacturer.
  • SM   NEW/Current.  For all 12/2004 and later automobile engines.
       An "Energy Conserving" motor oil (something good for late model cars, not most motorcycles). The API increased the standards for anti-foaming, increased detergent levels, and improved low-temp performance, while lowering the ZDDP package contents again. API SM now replaces API SJ and API SL -- but SM-rated oil is still not suitable for most motorcycle engines (just as SJ and SL rated ones weren't), especially virtually every air-cooled, oil-cooled and air-oil cooled motorcycle engines and ANY motorcycle engine designed prior to 2001 (such as Suzuki Katana 600/750/1100, Suzuki Bandit 600/1100/1200). Check your motorcycle owner's manual specifically for recommendation of an SJ/SL/SM rated motor oil before using API SM rated oils in your motorcycle! Do not use unless an API SJ, SL or SM rating is specifically called for by your motorcycle manufacturer.

Comments from the API in repsonse to our query, 11 Aug '05:
(Note this correspondence has been trimmed for length)
   Higher performance engine oils such as API SJ thru SM will contain some level of friction modifier. While the friction modifier improves fuel economy, it is not compatible with wet clutches used on motorcycles. The friction modifier causes the wet clutch to slip. This is especially true if the motorcycle manufacturer recommends using only engine oils carrying API SF or SG Service Categories.
   API recommends following the Original Equipment Manufacturer's (OEMs) oil recommendations. Typically an API SJ through SM engine oil would include some friction modifier. Only if the [motorcycle's] OEM indicates that higher performance engine oils such as API SJ, API SL and API SM it is possible to use these engine oils in these motorcycles.
Dennis L. Bachelder
American Petroleum Institute
1220 L Street NW
Washington DC 20005 USA

   Unlike the API, which is an petroleum-specific institution, JASO is a consortium of major vehicle manufacturers in Japan. JASO stands for the Japanese Automotive Standards Organization (although translated from Japanese it might be more accurate to say Japanese Vehicle Manufacturer's Organization). JASO rates oils for compatibility with their products (cars and motorcycles), and all the major Japanese motorcycle manufacturers (Honda, Kawasaki, Suzuki, Yamaha) specified a JASO standard for compatibility with their four-stroke motorcycles' oil needs starting in 1998, called the JASO-MA standard. Most non-Japanese motorcycle manufacturers (Aprilia, BMW, Ducati, Triumph, etc.) now also specify a JASO standard for use in their motorcycle engines.
   JASO only has two standards for four-stroke engines at this time: JASO MA (higher friction oils) and JASO MB (low friction oils). The JASO specifications include HTHS Viscosity requirements (covered further down on this page), sulfated ash content and a number of other important characteristics that are not specified or are not as rigidly specified by the API specifications.
Updated: JASO split their JASO-MA standard into JASO-MA1 and JASO-MA2. MA1 is the follow on for bikes that call for JASO-MA oils.
You can find more information on JASO MA-series requirements and the specifications in this JASO MA1/MA2-series Implimentation Document (PDF)

   If your motorcycle manufacturer specifies both an API rating (such as SH), and the JASO MA rating, use only motor oils that satisfy both of the standards listed (the packaging for the oil will carry symbols for both if it meets both standards). Do not use an oil that only meets one standard but not the other, if both standards are specified by your owner's manual or the motorcycle manufacturer. Note that Shell Rotella oils are not JASO MA certified as of the time I write this due to the high sulfated ash content (JASO spec is maximum of 1.2% by weight). If your motorcycle engine was build between 1980 and 1998, it will not have a JASO specification, but will benefit from using a JASO MA spec oil (in conjunction with whatever other specifications the manufacturer requires).


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Oil: Advanced Theory 3150

   Motor oil operates in a very hazardous environment, with great changes in heat, differing degrees of chemical exposure, and mechanical forces acting upon it. One of those forces is shear force, or forces which want to tear the actual molecules of the oil apart by mechanical means (this expecially applies to the polymer additive chains in multi-weight oils). When a piston suddenly changes direction in it's movement, the oil directly under the rings of the piston experience shear force. It also experience shear forces when it catches the edge of two gears interfacing with each other. In wet-clutch motorcycles, shear forces are also applied whenever the clutch engages, as oil on the surface of the friction plates is stretched by the two surfaces closing against each other. Additionally, oil exposed to the actual detonation event in the cylinder can be sheared by the force of the pressure wave from the explosion.

   Within an engine, many different conditions exist which chemically expose motor oil to other, undesirable chemicals. The most obvious one is gasoline vapors within the combustion chamber, some of which are driven into the motor oil coating the walls by the pressure wave of the detonation (imagine setting off a firecracker -- the pressure at the center of the firecracker will cause the paper, some of it still containing the gun powder in the firecracker, to explode outward; same concept). Since gasoline is formulated with a variety of different chemicals (or may have some of these chemicals in it natively), such as sulfur, MTBE, oygenators, et cetera, some of those chemicals also get "pressed" into the oil at the edge of the combustion wave. These chemicals combine with the motor oil that coats the piston's stroke range and often get carried away during the next piston stroke back to the oil reservoir (oil pan or sump). Some of the chemicals change their composition given the heat and pressure of the blast, when mixed with the hydrocarbons in the oil, and the results can include the creation of sulfuric acid from sulfur in the gasoline mixing with oxygen in the air or oil (which in turn can break hydrocarbon chains). And this is just the tip of the ice berg, so to speak, when it comes to chemical exposures.

   Motor oils can bind with oxygen in the air, a process known as oxidation, which results in a thickening of the oil into a sludge that is thick and gooey (and doesn't lubricate well or at all and is difficult for the oil pumps to move). The oxidation interaction also loses electrons in the process, which can act as a source for dielectric rusting or welding (accelerating the rust-binding of certain metals). Primarily this occurs with the paraffin wax content of the oil, which is why traditional dino oils tend to sludge up worse than synthetics (synthetics normally have very low or non-existant paraffin contents).
   The oxidation process is accelerated heavily by running hot (because high temps help facilitate oxydation of oils). Although you might imagine that the sludging can help offset viscosity breakdown (discussed in the next paragraph), the reality is that sludged oil coats the metals (reducing heat exchange) and reduces the total lubrication available to the actual metals (by acting as a barrier) as well restricting or clogging up oil passages (sometimes to the point of critical starvation).
For a good bit on sludge, take a look at Case Study in Sludge

   Previously we mentioned that the higher the base oil's viscosity, the better it is at fighting friction. Viscosity breakdown is the act of the oil's hydrocarbons being split, reducing the effectiveness of the oil's ability to deal with friction. If the viscosity breaks down too far, the oil simply won't protect the engine's friction surfaces any more (and you can readily imagine what that leads to -- metal on metal contact). Viscosity breakdown is one of the three primary reasons we change our oil in our vehicles, to replace the oil with oil that hasn't suffered yet (the other two reasons are suspended particles or contaminants which may induce wear on the friction surfaces, and oxidation, aka sludging).
   As anyone who watched TV during the 80's and 90's knows (from seeing Castrol GTX commercials), higher revving engines encourage faster viscosity break down. This is due to the higher incident rates of shear force exposures (faster turning of mechanical parts) and higher incident rates of chemical exposure (more detonations, etc), as well as a third source of viscosity breakdown: heat exposure. By comparison to car engines, motorcycle engines rev much faster and thus encourage viscosity breakdown even faster. And heat exposure is even more of a source of viscosity breakdown in air- and oil-cooled motorcycles than in water-cooled motorcycles (and far more than in car engines). Thus motorcycle oils are designed with this increased rate of viscosity breakdown in mind.

Where has my Viscosity Gone?
   In multi-weight oils, the viscosity breakdown causes the second number to decrease more rapidly over time than the base oil, because the long polymers sheer more readily (what starts as a 10W-40 will become a 10W-35, then a 10W-30, until it finally reaches a 10 weight baseline, effective 10W-10). Hopefully you will have changed your oil before it breaks down significantly.

   Although oil manufacturers don't tend to advertise their High Temp High Shear (HTHS) viscosity ratings, you can obtain them from most manufacturers by asking directly. This test is of how well the oil behaves as a lubricant at high speed under high stress and high shear while running under load at approximate full operating temperature for the oil (150°C). The higher the HTHS number, the better a job the oil does in preventing engine destruction under real world operating conditions, and the thicker the boundary layer of oil on a spinning bearing surface will build up. On the other hand, the lower the number, the easier a time the engine has spinning up (changing RPM's) because of the lower amount of work required to move the oil. As a result, you'll generally find lower HTHS numbers in oils that permit the engine to be a bit zippier, but you're trading off reliability for this power benefit.
Most motorcycle engines are looking for a minimum HTHS value of 2.9 (required for JASO MA & MB standards as minimum HTHS value). Like all forms of viscosity, HTHS values break down with use of the oil and degrade over time. Note that not all manufacturers HTHS values break down at the same rate under the same conditions, depending on the formulation of the oil, the viscosity stabilizers/enhancers used, and acid-neutralizers used.
Some comparison HTHS numbers for fresh oils:
Castrol R4 (5W40/USA) - 3.9
Castrol GPS (10W40/USA) - 4.1
Castrol GPS (20W50/USA) - 4.6
Amsoil Synthetic Motorcycle 10W40 - 4.2
Amsoil Synthetic Motorcycle 20W50 - 4.9 to 5.0
Mobil 1 MX4T (10w40/USA) - 3.9
Mobil 1 VTwin (20w50/USA) - 4.9
Redline Synthetic 10W40 - 4.7 (NOTE: No JASO-MA rating found)
Shell Rotella Synthetic - Greater than 4.0 (they wouldn't elaborate further even when we asked; note that no Rotella products are JASO-MA rated as I write this due to sulfated ash content levels).
NOTE: The /USA info is marked because these are values provided by the manufacturers for their US-market production oils listed; if the same oil is available in other markets, it may have different formulations and differing HTHS values.
ALSO NOTE: Valvoline's HTHS values are unpublished, but we have an information request in with them for this info (Mobil's is also unpublished, but a call to their tech-engineers provided the above answers).

   All motor oils have some temperature where they vaporize and/or spontaneously ignite, and then breakdown into other compounds. For most motorcycle engines under normal conditions, as long as this point is higher than the general engine temp and lower than the combustion & spark plug temperatures, it's not too much of an issue whether the flash point occurs at 380°F or 480°F (in such cases, the detergent load to wash away the by-products is more important).
   Motorcycles which are air-oil cooled or air-cooled (i.e. - don't use a secondary water cooling method to reduce heat), are a different story, and in these engines it can be extremely important that you use an oil with a higher flash point for the health of your engine. Additionally, any motorcycle engine that experiences certain extremely high-thermal-stress conditions, including racing, extended operations at temps above 95°F, and going from long-haul high speed interstate riding to getting caught in stop-n-go traffic (traffic jams or streetlight-to-street light city traffic) may need and can really benefit from higher flash point oils.
Some comparison Flash-point values for fresh oils:
Castrol R4 (5W40/USA) - 406°F (208°C)
Castrol ACT/Evo (10W40/USA) - 390°F (199°C)
Castrol GPS (10W40/USA) - 410°F (210°C)
Castrol GPS (20W50/USA) - 414°F (212°C)
Amsoil Synthetic Motorcycle 10W40 - 453°F (230°C)
Amsoil Synthetic Motorcycle 20W50 - 449°F (232°C)
Mobil 1 MX4T (10w40/USA) - 487°F (253°C)
Mobil 1 VTwin (20w50/USA) - 518°F (270°C)

   All major motor oils (motorcycle motor oils included), contain some degree of additives designed to help reduce (primarily) viscosity breakdown, by reducing or eliminating as many possible causes as is cost-effectively feasible. The major additives include Zinc, Phosphorus, Magnesium, Calcium, Boron. Additionally, various chemicals are added to operate as detergents, which help ensure contaminants stay suspended in the oil rather than adhering to surfaces. Then they often toss in something designed to help ensure oil seals stay healthy and swollen (so you don't get oil leaks). Plus they toss in some anti-foaming agents (to keep the oil from frothing as it's churned).
  And then some manufacturers also add graphite, teflon (PFTE), and/or molybdenum as an anti-wear agent, NONE OF WHICH (graphite/PFTE/Moly) ARE RECOMMENDED FOR WET-CLUTCH MOTORCYCLES; these last chemicals are also contained in many of the off-the-shelf oil additive packages like DuraLife and Extend50.

  • Zinc and Phosphorus -- the two primary metal anti-wear additives. Their purpose is to provide some degree of lubrication for metal-to-metal contact when oil pressure is too low (such as bearing surfaces while starting an engine). These two chemicals are usually packaged together by additive companies for the oil companies to use, as zinc dithiophosphate (ZDDP), and the oil companies add varying amounts to different formulations of their oils. Good for your engine, but high contents of it may foul catalytic converters if present. Note that motorcycles requiring API SF, API SG or API SH are not served by API SJ and API SL rated motor oils, as SJ and SL are lower in ZDDP quantities (and SJ/SL are car-specific, not rated for motorcycles by the API).
  • Magnesium, Calcium and Boron -- these are used as anti-corrosives, to prevent the formation of various chemicals which break down viscosity, including sulfuric acid. Neutralizing these acids helps keep the oil effective as a lubricant. The result is also that these chemicals help keep sludge and varnish from forming. Again, different motor oil manufacturers add different amounts of these chemicals to their various formulations (from none to lots).
  • Detergents -- too many possibilities to list, but they help ensure that by-products (varnish, sheared oil, dirt, dust, etc) stay suspended in the oil rather than adhering to the metal surfaces of the engine.
  • Graphite, Molybdenum (aka "Moly" aka molybdenum disulfide) -- appear in some automotive motor oils and many aftermarket oil additives, and unfortunately, in some motorcycle oils. These chemicals are good anti-wear, anti-scuffing additives, but are totally incompatible with motorcycles which have wet clutches!
       Note that molybdenum is normally used in anti-seize paste in the USA as the primary ingredient (the type you put on your spark plugs and wheel bolts).
  • Teflon (aka poly tetrafluoroethylene or PFTE) -- Teflon in specific is not intended for engines of any type according to it's original manufacturer (Dupont), and you should never use a product containing teflon in the oil system of any engine. Furthermore, it is 100% incompatible with any motorcycle using a wet-clutch.

A Motorcycle-specific Oil Standard:
   The JASO MA standard was passed in 1998 specifically for motorcycle engine/tranny requirements that weren't being met by solely the API standards. As a result, if your manufacturer has specified an oil that meets JASO MA and API SF/SG/SH/SH+SJ (any of these), it is critically important that you meet BOTH of those standards and not just one or the other. If you ride a Japanese motorcycle build between 1971 and 2005, and it calls for one of the following API specs (SD, SE, SF, SG and/or SH), then the JASO MA standard is recommended (but may not be required) -- as it will help keep your older motorcycle from encountering some of the problems that induced the JASO organization to create the JASO MA standard in the first place. This is expecially true for air and oil-air cooled high-RPM motorcycles. Note that JASO MB is a competing standard specifically for a different engine type, and does not replace nor supercede the JASO MA standard. Be careful to read the specs fully, as some oils claim to "exceed the JASO-MA friction standard" without meeting all of the JASO-MA specs.
   In 2008, JASO split the JASO-MA standard into two substandards: JASO-MA1 and JASO-MA2. If your needs called for JASO-MA, JASO MA1 is the follow-on standard for your bike.


What you really need to know...

   Changing your oil and filter by the recommended interval with an oil that matches your all of engine manufacturer's requirements is far more important than whether you use a dino oil or a full synthetic or something in between. If any of the following applies to you, change your oil more frequently than recommended by the manufacturer:

  • The motorcycle forms condensation where it's parked (meaning it also forms it inside the crankcase);
  • The motorcycle operates in a dusty environment (deserts, back roads);
  • The motorcycle operates in a high-humidity environment (85% or greater humidity);
  • The motorcycle operates in a high-temperature environment regularly (over 88°F / 32°C);
  • You tend to drive short trips (under 15 miles);
  • You tend to rev the engine a lot (riding close to redline);
  • You regularly get stuck in stop-and-go traffic or traffic jams or city driving in general (accelerates oil viscosity break down by up to 50%);
  • You drive irregularly (less than once every 4 days);
  • You should also change your oil immediately any time:
  • The motorcycle overheats or shows signs of overheating;
  • The motor oil gets contaminated with liquid gasoline.

   Although the motorcycle market is migrating to injectors, a lot of bikes out there still have carburetors. Anytime a motorcycle with carbs gets layed over (whether a high-speed spill or just a parking-lot drop), some of the fuel from the carb's float bowls will run down into the engine. Bikes with stuck carb floats can exhibit the same behavior. Gasoline robs motor oils of it's ability to lubricate and does not lubricate itself. Thus, any time you have liquid gasoline run into the oil, change the oil ASAP! Failure to do so is a good recipe for early engine failure and highly accelerated parts wear.

   Car oils are formulated for cars. Motorcycle oils are specifically formulated for motorcycles. Motorcycles induce accelerated viscosity breakdown, and thus motorcycle oils contain additives that car oils do not to correct for this. Additionally, many car oils contain additives which are not suitable for motorcycles with wet clutches; if you have a wet clutch (or aren't sure), always stick to good motorcycle oils.

   If you find out that you are lower than the low mark on your oil indicator and are stuck in the middle of Podunk with no access to motorcycle oil, use the best automobile oil you can get to top off, then change your oil & filter at the first available chance (back to motorcycle oil). In a pinch, we recommend Mobil 1 car oil, and although it's not our first choice in oils, it is compatible with all major motorcycles' oils in a pinch, and available at Mobil stations across the country 24 hours a day. Do not ride with less than minimum amounts of oil! Once you get to where you're going, change your oil (both because you used car oil and because what was there was too little at some point, implying it needs to be changed anyway).

   Use the weight recommended by the manufacturer of your motorcycle for the ambient temperature you will be riding in. Although thicker (higher viscosity) oils in theory reduce friction better, the difference in their thickness can also reduce the quantity of oil flowing past a bearing or between two tight surfaces, resulting in oil starvation at that point (and thus actually defeating the reason for using the thicker oil to begin with). Never use a thinner oil than recommended (i.e. -- if your specification calls for a 10W-40, do not use a 5W-40 in it's place).

   Not all oil filters are created equal by a far measure. Unless you have gone through the effort of cutting open an aftermarket filter and comparing the amount and type of pleating material and by-pass valve design to the one from the factory-spec oil filter, stick to the factory-specified oil filter. You know that your motorcycle was designed specifically to work well with the factory filter, and the couple bucks difference you might save in the short haul is not worth the wear difference over time.

   If you have a wet-clutch on your motorcycle, you need to remove the clutch pack before using any engine flush (such as Gunk "5 Minute Engine Flush"). If you have a dry clutch, this is not an issue, and we recommend using this flush if you notice any varnish on your engine internals or sludge deposits in your oil (especially as you change it). Changing your oil more frequently, and using a good grade of oil will help keep you from needing to use an engine flush product.
   NOTE: Some motorcycle engines have oil coolers and other reservior areas retain oil during a typical oil change (example: Bandit and GSXF engines retain up to 35% of the oil between the tranny, oil cooler and upper engine); when you do an oil flush on such an engine, you need to drain the cooler afterwards and do two oil changes in short sucession to each other (with 5 to 10 minutes of engine run-time between the oil changes). This will net you about 95% of the oil being renewed and gaurantee enough of the oil flush product has been cleared out. If doing this, change your oil filter at the time of the final oil change.

Oil Types Recommended:
   The most important thing is that you use a motorcycle oil with the specific ratings and weight that the engine manufacturer calls for (e.g. - API SF/SG, JASO MA, 10w40).
NOTE that API SJ, API SL and API SM do not replace API SH & earlier for motorcycle engines, so if your engine spec calls for API SH or earlier (such as SF/SG), you should not substitute in API SJ or API SL!
   The type of driving you do & the type of bike you ride obviously plays a role into the recommendation, but as a general rule of thumb for most bikes, we highly recommend any motorcycle-specific motor oil that complies with your required API spec for your bike and meets JASO-MA specs (exception: 2-strokes and motorcycles specifically designed to use API SJ or API SL rated motor oils -- which shouldn't use JASO-MA spec oils as a result). Personally, we use Castrol GPS 10w-40 and 20w-50 as a cost effective, well performing synthetic-basis oil -- one that we've personally used for eons. We also have verified reports of a Honda CBR rider getting over 200,000 miles out of his engine without any oiling-system related damages, nor burning any significant amount of oil at the end of this time (less than 1/4 cup per 3,000 miles at 200,000 on the odo) using only this type of oil.

   Several of the Japanese motorcycle manufacturers sell their own "house" brand of oil through their dealer networks. In some cases, these house brands have recently been reformulated to API SJ and/or API SL, which may not be compatible with your motorcycle (specifically, if your motorcycle engine calls for API SH or earlier, such as an API SF/SG rating). Suzuki brand motor oil is a perfect example; their standard 10w40 formulation recently changed from being API SF/SG to being an API SL-rated oil, which is thus unsuitable for most older bikes, and even some of Suzuki's newest models (such those which are air-cooled and/or air-oil cooled - such as '00 - '05 Bandit 600, and '98 - '05 Katana 600 & 750 engines).


The Analogy Tale... Toothpicks and Oil
   To put this all in a way that most laymen can readily understand:
   You start out with a pile of toothpicks (which represent the carbon chain lengths of oil). With a synthetic, they should all be the same ideal length; with a traditional dino oil most of them will be the length you want, with some shorter & a few longer bits in the pile.
   Your teeth are going to represent the engine/tranny/clutch -- the idea is to keep your teeth from touching by putting the toothpicks on the top surface of your teeth as you chew (engine turning) while holding them with your fingers (because your mouth is facing the ground, head tilted forward). And you don't get to select the toothpicks -- you pickup a bunch of them blindfolded each time. The teeth (engine/tranny/clutch) chop up or mash the toothpicks to some degree or other, leaving behind shorter pieces. If the pile ends up with too many short pieces, the toothpicks are useless because they won't keep your molars from touching. If you get too many short pieces, you might inhale them and choke (representing oil gunk build-up in the engine passages). If the toothpicks get too soggy, they won't work well either (representing build-up of viscosity-reducing pollutants in your oil).
   When you change your oil, you are removing some of the toothpicks and replacing them with new ones. Some bikes can drain all their oil in an oil change; many other brands have designs that only change out a certain percentage each change (Suzuki Katana's and Bandit engines come to mind; they change about 65% with each regular oil & filter change).
   So, the question is how can you best keep your teeth from touching? The best answer is still to replace the toothpicks on a regular basis so you have sufficient long ones every time you pick up some toothpicks.

Additional readings:

"Is this the Right Oil for my Bike?" by Jeffrey P. DiCarlo, September 1999, for the Internet BMW Riders.
"Oils Well That Ends Well" By Don Smith, Originally published in Sport Rider, August 2003.
"The myths, facts, and mysteries of the slippery stuff that keeps your engine happy." By Gordon Jennings, Originally published in Motorcyclist, October 1996.
JASO MA1/MA2-series Implimentation Requirements & Specifications for Compliance (PDF) Practicing Oil Analysis: Lubrication breakdown
"How Oil Refining Works" at How Stuff Works.
Kit Sullivan's Oil info (BOSS-302 Registry)
Bob Is The Oil Guy Website
NOTE: Obsolete Links have been removed and/or updated (Feb 08)


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