For years I used 92, then 93 octane in my cars. In the past, it always seemed that my cars ran better on the supreme unleaded.
When I bought my Contour new I asked specifically about the octane. Of course, 87 is the one the owner's manual suggests. Plus, the service advisor at my dealership reminded me that the computer in the car is designed to operate with 87 octane.
Getting to the point, I have tried several tanks of 93 octane in my Contour without much result. The main thing I was looking for was increased fuel mileage - if anything, it went DOWN! I know that sounds crazy, but it's true. I seem to get better gas mileage from the 87 octane regular fuel. I can't seem to feel much of a performance increase either, but nonetheless when the last autocross came up, I had 93 octane with an octane booster just in case it decided to work.
I'd say go with at least 3 consecutive tankfulls of 93 and keep track of your MPG. Listen for pinging, knocking, etc. and try to feel for performance gains. If you like the premium results, stay with it. If, like me, you find that the MPG isn't improved and that no real differences manifest, go with the cheaper choice.
Many happy miles . . .
