A reader asks: My Suzuki V-Strom 650 asks for 10W-40 oil. My motorcycle is used for street, touring and light adventure riding. Some V-Strom owners run the AMSOIL Dirt Bike 10W-40 in this model, while others run the Metric 10W-40. What is the difference between the two and what is the best choice for my motorcycle?
Our answer: Both the AMSOIL Metric Synthetic 10W-40 and AMSOIL Dirt Bike Synthetic 10W-40 offer world-class protection, performance and smooth shifting. However, there are some very important distinctions between the two. Let’s take a look.
The Metric 10W-40 has a longer service life than the Dirt Bike 10W-40. The Metric 10W-40 product was designed to stay in service for up to two times the OEM-suggested drain interval or one year (whichever comes first). AMSOIL “overbuilt” this product so that it could withstand big touring miles.
The Dirt Bike 10W-40 is designed to go the full service interval as suggested by the motorcycle manufacturer. Unlike the Metric Oil, it is not designed for extended drain intervals. The reason being is that the oil is changed more frequently in motocross and dirt bike applications. However, the Dirt Bike Oil can certainly stay in service for the entire service interval as suggested by your owner’s manual. This does not imply that the Dirt Bike product is “underbuilt”. It designed to withstand the severe thrashing delved out by dirt bike engines and transmissions.
Discerning riders may notice subtle clutch engagement differences between these two products. AMSOIL Dirt Bike 10W-40 is designed to deliver slightly more aggressive clutch engagement. The reason being is that motocross bikes require instant clutch engagement during race starts and in tight off-road situations. The Metric Oil is designed to deliver smoother clutch engagement which would be more desirable on the street.
It is important to note that both of these synthetic motorcycle oils are 100% wet-clutch compatible. As they both promote cooler operation, longer clutch plate life can be expected. There is no risk of clutch slippage when switching from a conventional motorcycle oil to one of these AMSOIL Synthetic Motorcycle Oils.
It should also be noted that AMSOIL Synthetic Motorcycle Oils have a reputation for optimizing shifting smoothness. They can also ease shifting into neutral.
Both products have been torture-tested in professional racing and on the test bench. The AMSOIL Metric and Dirt Bike 10W-40 oils offer world-class engine and transmission protection. There is no wrong answer between them in this category.
Both the Metric and Dirt Bike Oils contain rust and corrosion inhibiters. However, as the Metric 10W-40 product is designed for longer service intervals, it is a bit more robust on this front.
The total base number of each oil gives us a hint regarding corrosion fighting ability. Total base number (or TBN) is a motor oil’s capacity to withstand acidity. The higher the total base number, the greater the capacity to battle acids. The Metric 10W-40 has a very high TBN of 11.6. Dirt Bike 10W-40 has a respectable TBN of 7.6.
While TBN doesn’t tell the entire story regarding corrosion resistance, it does give us a good indication. Again, as the Metric 10W-40 is designed for ultra-long service intervals, a high TBN is a great asset.
Meanwhile, the Dirt Bike Oil is designed to provide wear control in the dirt bikes and motocross bikes that are routinely pushed to the very limit. However, the drain intervals are generally not that long. Therefore, having an ultra-high TBN is redundant and not a requirement in dirt bike applications.
Both the AMSOIL Dirt Bike and Metric oils will work exceptionally well. However, based on the street/touring/adventure usage, Metric 10W-40 gets the edge. The longer service life is a better fit for bigger miles. The smoother clutch actuation may also be a plus in stop and go traffic.