At least you guys weren't arguing too much.

I'll stick with Shell. I've already put Seafoam in my car, and ran in nonstop untill dry. I think mpg is a little better. The car runs just the same though. I never put 87 into it, and as far as I know, this C280 never seen regular in its tank. Anyone knows if Amoco adds any cleaners to its premium?

And, of course, thanks to everyone for the input!