A reader asks: I have a 2017 KTM 300 EXC. The manual calls for 15W-50 oil in the transmission. I see that AMSOIL has the Metric Synthetic 15W-50 Motorcycle Oil and the Synthetic Dirt Bike Transmission Fluid. Which is the best option for me?
Our answer: We have a third option that we think would be the perfect transmission fluid for your 2-stroke KTM. That would be AMSOIL 10W-50 Synthetic Dirt Bike Oil. We’ll explain why below.
Let’s take AMSOIL Synthetic Dirt Bike Transmission Fluid off the table for your application. The Dirt Bike Transmission Fluid was designed for Japanese-brand dirt bike applications that require an SAE 80 oil. Keep in mind that gear oils use a different viscosity scale to prevent confusion with motor oil. An SAE 80 gear oil is actually the equivalent of 30-weight motor oil (in terms of actual viscosity). Your model requires a heavier 50-weight viscosity.
AMSOIL Metric Synthetic 15W-50 Motorcycle Oil would certainly perform and protect very well. There would not be any harm in using this product. Metric 15W-50 is designed to deliver smooth clutch engagement in street bike applications. Again, it will work, but the Dirt Bike 10W-50 is designed for off-road service.
An Ideal Transmission Oil For KTM Dirt Bikes
AMSOIL 10W-50 Synthetic Dirt Bike Oil was designed for dirt bike transmission service. It fights clutch fade by dissipating heat. This allows for maximum clutch plate preservation. It also provides instant clutch engagement in tight off-road situations. Dirt bike transmissions are commonly put under extreme loads in mud, deep sand and other extreme conditions. This aspect was a main focal point during product development.
AMSOIL Dirt Bike 10W-50 will also protect gears during rapid shifting. The 100% synthetic formula provides smooth, optimized shifting performance.
Replacing a 15W-50 with a 10W-50 is a non-issue. Keep in mind that at operating temperatures, both products are a 50-weight oil.
In conclusion, AMSOIL Dirt Bike Synthetic 10W-50 was designed to hold transmissions together under the rigors of professional motocross racing. Therefore, it will be the perfect upgrade for your bike too.