Originally Posted By: Jeffs2006EvoIX
COSTCO is ARCO brand gas and my cars get about 2-3 mpg's less on this fuel. Why? I have no idea, the additive pack or something my cars just dont like. Even my old Dodge Caravan will ping on COSTCO 87 but not ping on SHELL 87 so???
Costco fuel has a very good additive package, it's Top Tier certified. In Canada it's even better, as Costco premium has no ethanol in it here. I'm not super picky about what fuel I put in the BMW or Honda but I'm going to make sure I always run Top Tier in my new Corvette and also ethanol free too (except when travelling to the US as that'll be more difficult to find on road trips). I figure that by using Top Tier fuel from day one it will pretty much ensure I never need to add any fuel system cleaners.