I ride Raptor 700. I am wondering what oil to use in high heat environments like sand dunes in the summer. I usually use Formula 1 10W-40. I'm wondering what the difference is between something like 10W-50 and 10W-40 what is best to use in winter and what is best for summer and high temperature environments.

 

I use 5w 40 Rotella T6 in all my quads and motorcycles. It is compatible with the wet clutch.

 

X2 on Dazeys recommendation...look at you manual and see what the factory recommends. As long as it meets factory weights and is a full synthetic, all temp ranges will be fine. I pretty much use the 5-40 full syn in all my toys and have for years with O issues.