Sorry but comparing automotive engine oil to Motorcycle oil is like comparing apples to oranges. Motorcycles (for the most part) have wet clutches, automotive engines (for the most part) DO NOT. You wouldn't put 10w40 engine oil in your automatic transmission of your car, so why run it through the clutch of your motorcycle. Only use a JASO MA classified oil. MA is the designation for motorcycles. And on a personal note I race a 2006 KX250F and a 2006 KX450F and I use Castrol R4 superbike oil in them both (Changed about every 8-10hrs) and have since there second oil change(broke engines in on KAWACHEM 10w40). I have put 2 top ends in the 250 and one in the 450, they both have about +/- 80hrs on them, and on all three rebuilds the engines looked great. And I have only had to shim one valve in the 250F. I chose to run the Castrol R4 because that is what the Kawasaki Factory teams run. Now I'm not saying that its the best oil or that there aren't other good oils out there I'm just saying to make sure its designed for a motorcycle.