My brother has a honda atv sportrax 250 ex. I might be buying it off of him, he wants a 4x4 atv. Its air cooled, has the typical shared engine/tranny oil set up and has an auto clutch. He uses 10w40 castrol gtx in it. He is the type that wont read anything, just blurts out, I was told not to use synthetic, it will mess the clutch up. With no owners manual around to prove anything to him, does anyone know the oil honda specs for them?