I'm looking for some feedback from anyone using a full synthetic oil for their WR. I own a new 2000 WR400F and I am using Yamahalube 10w50 semi-synthetic. Is anyone using Mobil 1 15w50 full synthetic in the gray bottle? I know Mobil sells a motorcycle version of Mobil 1 but they are in the black bottles and sell for twice the price. A local Yamaha mechanic said using a straight synthetic will burn up the clutch. Any feedback would be appreciated.