I buy the gas that my car recommends. In my people hauler(we've 7 in the family) I run 87 octane at the cheapest price feasible. In my commuter car(2.0 turbo) i

I buy the gas that my car recommends. In my people hauler(we've 7 in the family) I run 87 octane at the cheapest price feasible. In my commuter car(2.0 turbo) it wants e85 or 91 octane. Texas sells 89 or 93 octane so I buy 93, with an occasional 89. When I want to get 10% more horsepower for 2/3rds the fuel economy I buy E85. Price doesn't have any effect on what I purchase. I think it only would come into play if regular was 1.85 and premium was 4.00.