Viscosity has traditionally been a motor oil's major friction-fighting property. But along with many other things, viscosity has become less a part of reducing wear in modern times. All the same, engineers continue to somewhat rely on that characteristic of an engine oil. It is interesting that an oil’s viscosity thickens when the oil is cold and thins when it is hot, becase this is exactly the opposite of what the engine needs. This is why multiviscosity oil was developed. Multivis motor oil addresses the changing viscosity problem by being chemically treated to thicken less when cold and thin less when hot. Pretty neat, this. A 10W-40 oil for example, will thicken no worse than would a 10 weight oil under cold conditions, and thin no worse than would a 40 weight under hot conditions. Multiviscosity oil isn't oil with multiple viscosity behaviors, rather it's oil whose viscosity is less affected with temperature. It has a high "viscosity index", say the engineers. On a right-angle, X and Y temperature versus viscosity graph, the multi-vis is depicted by a line closer to horizontal, while all single-weight oils have astonishingly very nearly vertical lines of viscosity change with temperature.

Motor oil has a tendency to boil away into a gas when churned and heated. The industry standard allows up to 15 percent, and powersports engines are mostly right at this limit. In fact, powersports vehicle oil consumption happens mainly due to vaporization, and hardly at all due to burning in the combustion chamber. Today's motor oil must also contain anti-foam agents, corrosion inhibitors, antioxidants—chemicals that fight the interaction of the oil with oxygen that can form sludge—and other ingredients designed to "keep house" within the engine. There are even detergents that scour up contaminants, and dispersants that keep these contaminants in solution until they can be emptied out with the oil change. Without all these hard-working additives, modern motor oil would simply be useless. And engine oils have had these additives since the late 1940s, at concentrations that have increased every few years since then, thanks to the API (American Petroleum Institute) and their “service” designations—determined in cooperation with automotive OEMs and influenced by the OEM’s warranty provisions.

In the early days of non-conventional motor oils, the most exotic examples got all the press. Oils touting graphite or Teflon and other exotic oils claiming miracle abilities to “replate” engine parts quickly came to represent, however inaccurately, the then-new synthetic lubricant industry. Unfortunately, in the face of this "snake oil" spectacle, honest hard-working synthetic motor oil products were overlooked, and trust was slow in coming. Today, powersports OEMs themselves sell their own synthetic motor oils, and the situation has ultimately leveled out. Synthetic motor oils came of age so to speak. Synthetic motor oil is made very differently than petro oil. The lubrication 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—an ester, a sort of greasy group of molecules. Then this base stock is built back up using high-end petroleum and chemical compounds. The result is a base stock that already, without additives, is superior to the additive-laced finished petro oil product. Because the base stock is synthetically built, basic lubricating properties such as viscosity index and volatility control are already built-in, making this oil better at handling heat and at resisting vaporization. In fact, synthetic oil’s viscosity index is so good it is used in the Antarctic. The better base stock also eliminates the need for the load of additives that petro oil requires, meaning that there is less "junk" swimming around in the oil to take up space and wear out quickly. And it is in fact the additives that wear out first, not the oil.

Honda engines use one lubricant to lubricate parts that in other kinds of vehicles—most notably cars, Harley-Davidsons, and many Euro bikes—are lubricated by two or three different oils. Unfortunately, the automotive industry drives the engine lubrication world. That is, it calls the shots—it determines the rules. In 1998, the Environmental Protection Agency (EPA) forced engine lubricant producers to add friction modifiers in an effort to reduce exhaust emissions. Yep, more fuel economy equals less exhaust emissions. Leave it to the feds to think of that one. However, this friction-modified oil is incompatible with Honda clutches, whether friction or sprag type. The Japanese OEMs notified all of their dealers of this problem and of their solution in service bulletins, and at the same time developed an exemption. This new standard, JASO MA, is an override of the EPA’s mandate and identifies the only oil you should be using in a Honda. Everyone has their preference and their opinion, but this MA thing is not subjective as are those things. It’s objective. It is a must. Look for the MA designation on the bottle. This is one of your most critical choices regarding engine oil. Many oil suppliers now claim they meet JASO MA requirements but without the designation on their containers. That may be, but I would rather stick with the MA label.

But there is something else even more important than avoiding friction-modified oil, as utterly important as that is. My lifelong experience in this industry says there are always some folks who will let their oil level get too low. It's very common. Innumerable customers over a period of more than fifty years have proven this. Check the level often. Run the engine for a minute before determining the final level during refilling—don't just measure it in. If you have an oil cooler, best practice is to check the level before the cooler has had time to drain down into the crankcase and give a falsely high reading. The simple fact is, the single most important thing to remember about your engine oil is keep enough in there. Ask any powersports mechanic. In the repair shop, it is many times more common to see issues connected with the lack of oil and with oil that has never been changed, than it is all the other engine oil variables combined.