I had my tranny apart a few month's ago to replace the bottom rod bearing's and rod,I ate up the BOTTOM rod bearing they were totally gone out of the cage i replaced it with the 01 bearing different part number. I guess They had a problem with them funny, i never had a problem with my 98.Anyways my friend who did my bottom end also was looking at my tranny he was amazed how the tranny looked ,shift forks had no marks what so ever on them, gears were awsome.I have been using mobil 1 15/50 since day 1.colder weather though i would get some drag.I been using belray just because of the drag issue,But my tranny looked so excellent i wanted to go back to the mobil.SO yesterday i say what the hay let me try the 10/30 What is the worse my clutch will slip.The 10/30 bites as hard as the15/50 no slippage at all.I was in some sand, uphills ,corners.I rode for 2 hrs hard with no slippage at ALL.I REPEAT THE CLUTCH WILL NOT SLIP.no drag either.