Occasionally someone asks me why they can’t just put regular motor oil in their motorcycle. The short answer is that oils are formulated for specific applications. Motorcycle engines and automobile engines function differently, and the lubricants that service them have different needs. Here are six primary differences between motorcycle and automotive engine applications.
1. Operational Speed: Motorcycles tend to operate at engine speeds significantly higher than automobile engines. This places higher stress on engine components, increasing the need for wear protection. Elevated operating RPMs also promote foaming, which can reduce an oil’s load-carrying ability and accelerate oxidation.
2. Compression Ratios: Motorcycles tend to operate with higher engine compression ratios than automobiles. Higher compression ratios place additional stress on engine components and increase engine operating temperatures. Higher demands are placed on the oil to reduce wear. Elevated operating temperatures also promote degradation of the oil, reducing its life expectancy and increasing the formation of internal engine deposits.
3. Horsepower: Motorcycle engines produce nearly twice the horsepower per cubic inch of displacement as automobile engines. This exposes the lubricating oil to higher temperatures and stress.
4. Variable Engine Cooling: Many motorcycles are air-cooled or use a combination air/oil design. Though effective, they result in greater variations in operating temperatures, particularly when motorcycles are operating in stop-and-go traffic. Higher operating temperature promotes oxidation and causes oils to thin, reducing their load carrying ability.
5. Multiple Lubrication purposes: In automotive applications, engine oils are required to lubricate only the engine. Many motorcycles have a common sump supplying oil to both the engine and transmission. In such cases, the oil is required to meet the needs of both the engine and the transmission gears.
6. Inactivity: Motorcycles are typically used less than automobiles. Motorcycle use is usually periodic and, in many cases, seasonal. These extended periods of inactivity place additional stress on motorcycle oils. In these circumstances, rust and acid corrosion protection are of important concern.
So, while the debate over which brand of oil to use will surely rage on, the debate over which type of oil to use is largely settled once you understand what makes the oil used in motorcycles different than the oil used in your car.
