The Nature of Motor Oil
Motor oil is of course a lubricant. To lubricate is to reduce friction, so the first and foremost desired quality of any engine oil is friction reduction -- keeping moving parts separated. That in itself presents problems, of course, but we'll get to that in a bit. Besides lubrication however, motor oil is burdened with many other tasks. For example, the oil must also fight corrosion, cool, seal, and clean. A lot could be said just about these five things, because they are a lot to expect from an oil. In fact, the wonder of modern engine oil is that it performs these many wonders despite having several significant handicaps, just a few of which we'll address here. First, while an oil's viscosity has traditionally been viewed as its major friction-fighting property, that viscosity invariably thickens when the oil is cold and thins when it is hot. This is unfortunately exactly the opposite of what an engine needs the oil to do. So right off the bat, motor oil is falling down on the job. Multiviscosity motor oil addresses this very fundamental problem to a degree, by having chemicals added to it (long-chain molecules called polymers) which cause it to thicken less when cold, and thin less when hot, that is, less than the oil would if it were a straight weight oil. Interestingly, these polymers "unwind" when hot, resulting in increased viscosity. The fact is, the basic definition of the multi-vis oil is that its viscosity index is above a certain very high point, that is, its resistance to viscosity change due to temperature is much less than that of a single-weight, unmodified oil. On a graph, the multi-vis is depicted by a straigher line, while all single-weight oils have steeper lines of change. The dual designation in a multi-vis oil, besides being a tip-off that it is multi-vis, communicates these temperature characteristics at temperature extremes. With a 10W-40 for example, the oil will thicken no worse than would a 10 weight oil under identical cold conditions, and thin no worse than would a 40 weight under the same hot conditions. The "W": by the way stands for winter (not weight. The winter designation is the result of a 0 degree F test procedure. The second number, in this case the 40, is the viscosity tested at over 200 degrees F. Another one of motor oil's significant drawbacks is that it is to varying degrees quite volatile, meaning that it has a tendency to boil away into a gas when churned and heated. In fact it does this readily in high rpm, high temperature powersports (motorcycle, ATV, scooter, snowmobile, personal watercraft, and utility vehicle) engines. It is not widely understood among users, but oil consumption in powersports engines, when observed, is due much more to oil vaporization than to the oil's burning in the combustion chamber. Interestingly, the engines which vaporize their oil the most are those in single-cylinder, high-output off-road bikes. A third issue in the motor oil world is that the high output engines found in most powersports vehicles also mandate the addition of zinc and other anti-wear agents in today's oils, because unaided, these oils just aren't inherently up to the task. More about that later. And finally, in order to do more than simply lubricate, today's motor oil must also contain anti-oxidants, anti-foam agents, corrosion inhibitors, and other ingredients designed to "keep house" within the engine. For example, detergents are added to scour up contaminants, and dispersants are included which keep these contaminants in solution until they can be emptied out with the oil change. Without these many hard-working additives, modern motor oil would simply be useless. And all this is just the beginning.

Additives
Clearly, petroleum motor oil’s fossil material base stock is by itself far from adequate to meet modern engine lubrication needs. Additives must be included to the base oil to make the final product perform as desired. Unfortunately, these chemicals don’t actually improve the oil, they just temporarily change its behavior. These additives eventually wear out, and when they do, the oil must then carry this "dead weight" around. This is the number one drawback of conventional, petroleum-based motor oil. Its strength comes from ingredients that do not last as long as the oil itself lasts. This, incidentally, is why racers often prefer single-weight motor oils. They do not break down into lower viscosity grades as quickly as do multi-vis oils. But don't confuse the racer's needs with yours. One-day use is very different from starting and stopping, temperature extremes, and other variables that the racer does not encounter.

Synthetic Motor Oil
There is much that is misunderstood about synthetic motor oil, and controversy and misinformation continues to surround it. In the early days of the synthetic motor oil industry, the most exotic examples got all the limelight. Oils containing graphite and others claiming miracle engine parts "re-plating" abilities quickly came to represent the synthetic lubricant industry. Unfortunately, in the face of this "snake oil" spectacle, honest hard-working synthetic motor oil products were overlooked, and trust in really good synth motor oils was slow in coming. Today, powersports OEMs themselves sell their own synthetic motor oil, and the situation has ultimately leveled out. Misunderstanding still remains however. In order to understand what synthetic motor oil is, it helps to first consider how conventional petroleum motor oil is developed. Petro motor oil production starts when crude oil is separated into several different products, including propane, diesel oil, and other things. Two kinds of lubricating oil are also produced, distinguished primarily by their viscosity and volatility. One of these two "base stocks" is then purchased by a motor oil developer, who adds to the base stock a commercially purchased package of lubricating oil additives such as were described earlier (i.e. anti-wear, anti-foam, corrosion inhibitor, etc.). These additives give the base stock attributes it did not have before, and make it more suitable as an engine lubricant. As already mentioned, the additives are short-lived, and vary from retailer to retailer, making petro oil an oil with a self-destruct timer built into it. Synth motor oil on the other hand is made very differently. The petroleum scientist starts with the same base stock, but he kind of reverse-engineers it. He breaks it down chemically into its molecular parts. The petroleum is divided, and divided again, until the remaining part is the smallest piece that still possesses lubricating quality. This piece is an ester, a sort of greasy group of atoms. Then the scientist rebuilds the base stock with high-end petroleum and chemical compounds that have the qualities he wants in a motor oil. At this point it's still just a base stock, but the result is a base stock that already, without additives, is superior to the additive-laced finished petro oil product. This base stock is then sold to the motor oil developer who adds and tweaks until it is a complete synthetic motor oil suitable for his label. Because the base stock is so good however, very few additives are needed. Two things result from all this. First, because the base stock was synthetically built, basic lubricating properties such as viscosity index and volatility index are extremely good, making this oil potentially better at handling heat and at resisting vaporization, to name just two qualities. Second, the superior base stock eliminates the need for the huge load of fancy additives that petro oil requires, meaning that there is less "junk" swimming around in the oil to take up space and wear out quickly, resulting in an oil that is more, well, oil, and one that lasts longer. In fact, higher heat carrying ability and fewer required change intervals remain two of the synth oil's major attributes even today. Incidentally, a good synth oil also has more pourability, meaning that it pours easier at cold temperatures, which is why it is used in equipment on duty in the Antarctic.

Special Powersports Issues
However, whether you use petroleum or synthetic motor oil isn't really the most important issue. The fact is, there are certain special powersports engine oil needs you should be aware of.

Common Engine and Transmission
First, unlike cars, most four-stroke powersports vehicle engines combine the engine and transmission together in one housing. Consequently, these engines use one lubricant to lubricate parts that in other kinds of vehicles, most notably cars, are lubricated by two or three different oils. Unfortunately, the automotive industry drives the engine lubricating industry by and large. That is, the auto industry calls the shots, and determines the rules. The problem is, in recent years, the Environmental Protection Agency (EPA) has forced the engine lubricating industry to make motor oils that are so slippery they actually can improve the fuel economy in car engines, which is in essence an emissions issue. However, the motor oil companies are using friction-reducing chemicals in these modern auto lubricants to make this happen. These friction modifiers are highly incompatible with the oil-bathed clutches and sprags (one-way bearings) that are used in most powersports engines.

High Engine Output
The second consideration is the powersports vehicle's high specific engine output. On average, our engines deliver more power per cylinder displacement than do all but a few specialized car engines. This higher specific horsepower demands a lubricant with high amounts of anti-wear agents. Unfortunately, automotive motor oil makers are systematically reducing anti-wear agents such as zinc.

High Engine Rpm
Third, there is the powersports engine’s higher rpm and higher temperatures. The use of thinner, higher volatility automotive oils results in excessive evaporative loss in powersports engines, leading quickly to oil consumption related engine failures.

The Solution
These are very real needs of a very specific industry, the powersports industry, and they are now at odds with the objectives of the automotive industry. Because of this, the powersports industry in 1998, after recognizing that the auto lubricant industry is no longer supporting the powersports market, established special powersports-specific motor oil standards. In effect, all powersports vehicle manufacturers today categorically (through service bulletins) bar the use of today’s automotive spec motor oil, from API (American Petroleum Institute) classification SJ and forward, in their products. This new standard is known as JASO, and it specifies completely new motorcycle motor oil parameters which address the powersports vehicle’s special lubrication needs, particularly in the areas of friction and wear. The JASO motor oil classification of most interest to us is JASO MA oil.

Conclusion
The bottom line? Just remember three things. First, use a multi-vis oil within the viscosity ranges specified in your owner's manual. This will be 10W-30, 10W-40, 20W-40, or 20W-50. Don't for example use a 5W-30 motor oil. Second, this oil can be either petroleum or synthetic, but should not include any exotic material additives. Finally, chose an oil with an API service rating of SH or earlier, or if it has a later API service rating such as the current SL classification, it must also be labeled JASO MA to designate that it was developed without the automotive-mandated friction-reducing components that are a standard part of the API's latest specification.

Q: IS AUTOMOTIVE MOTOR OIL BAD FOR A MOTORCYCLE?

A: Not bad, but probably not the best. Why not? It is designed in reverse order to a motorcycle oil. The priority hierarchy of automotive motor oil is: (1) Maximize fuel economy. (2) Reduce emissions. (3) Offer protection for the moving parts. Today's automotive motor oils do not have the same degree of extreme pressure and anti-wear agents that they did just a decade ago.

Q: WHEN WAS AUTOMOTIVE OIL AT ITS BEST?

A: Oil changed ten years ago when automakers were pressured to clean up the air. Since 1993, the entire automotive industry has worked to reduce exhaust emissions. Automotive motor oil must adhere to the performance categories set by the American Petroleum Institute (API). These are called the API Service Categories. The API categories have been around for 50 years, but for the first 35, the categories were upgraded six times to meet the demand for higher engine performance.

The current American Petroleum Institute (API) designation is SL. The API SL oils are designed to provide better high temperature deposit control and lower oil consumption. SL oils are missing important agents that improve extreme use lubrication. In their place are friction modifiers that improve fuel economy.

Q: WILL AUTOMOTIVE MOTOR OIL HURT MY BIKE?

A: It could. If you're using an automotive motor oil in your racing four-stroke, you're not buying the best protection. An API SM/SL oil is missing vital anti-wear components: the most common being zinc, phosphorus and sulfur. These agents are harmful to the catalyst that is used to diminish the level of pollutants in automobile exhaust.

Q: WILL AUTOMOTIVE OIL HURT MY CLUTCH?

A: Yes. The friction modifiers in motor oil improve fuel economy by making it easier for the gears, bearings, pistons and rings to slip, slide and turn inside the engine. Unfortunately, these friction-minimizing agents also make it easier for the clutch in a motorcycle to slip. If you are using automotive motor oil in your bike, apart from CRFs, you are losing hook-up and acceleration, as well as reducing the life of the clutch.

Q: WHY SHOULD I MEMORIZE THE ACRONYM "JASO"?

A: As soon as it became apparent that the American government was mandating economy over protection, the Japanese Automotive Standards Organization (JASO) developed a standard specifically for performance fourstroke motorcycles. JASO designates two different four-stroke oil classifications: MA and MB. The MB oil is low friction and the MA is sans the friction enhancers.

Q: WHY ARE MOTORCYCLE SPECIFIC OILS BETTER?

A: Motorcycle specific oils are pumped up with five times the anti-wear, anti-scuff and extreme pressure additives of regular motor oil. As an added plus, motorcycle oil does not include molybdenum disulfide and other friction modifiers that wreak havoc on clutch performance.

Maxima, a popular motorcycle oil supplier, starts with an API SG Service Category base oil, the last formulation that wasn't regulated as to the amount of zinc-dialkyldithiophosphate (zinc, phosphorus and sulfur) it could contain. Maxima then boosts protection through a proprietary mix of performance additives. The end result is a motorcycle oil that doesn't break down under extreme heat and is tough enough to cushion meshing gears.

Q: WHICH FOUR-STROKE RACING OIL SHOULD I USE?

A: If the bottle of oil doesn't list that it is an API SG Service Category or JASO MA spec, it's not good enough for your motocross bike. Although a bottle of oil might say "motorcycle specific" or "safe in wet clutches," the best endorsement is the API SG or JASO MA designation. It's better to be safe than sorry.

There is a caveat that applies to CRF owners, however-which we will clear up in a few paragraphs.

 

Q: WHAT VISCOSITY SHOULD I USE?

A: The most popular viscosity is 10w40. It's thin enough not to bog down the crank and offers ultimate protection under an extreme load. Every owner's manual lists the recommended oils, brands and viscosities.  Harley recommends  20w 50 for most climates.