Dont worry, I run Amsoil synthetic in all my toys (except my Scarab, when the Merc O/B gets rebuilt I will use it then). Use either their 0W-30 or the heavy duty 5W-30. Mostly the 0W-30 though, and my TrailBlazer loves it. Epic will be getting an oil change here in about a week (when I get it back home from storage in Coeur d' Alene) using all Amsoil stuff and the Universal ATF in the trans as well.