Like I didn't have enough to worry about!! Will the STP muck up the engine and or leave deposits? There was an article in Circle Track Magazine talking about the same thing. They spoke with Comp Cams too. Comp is recommending the diesel oils such as Shell Rotella, Mobil Delvac, Chevron Delo and Castrol Tection. I looked briefly at the Rotella site. Rotella makes a syntehctic 5-40 that has all the Comp recommended API ratings: CI-4 Plus; CI-4 and CF-4. So it has the
zinc, but how will it stand up to heat? I assume it would be OK being a
synthetic, but what do I know.
EDIT I invited the Shell Guy (Rotella forum moderator) to visit us and share his knowledge about Rotella. With hope he will join the discussion. He posted the Comp Cam article a while ago on the Rotella forum.
http://www.rotella.com/ubbthreads/sh...c=1&PHPSESSID=