Originally Posted by Maxwell
I'm sorry but you are wrong there. I've used the cheap stuff 87 octane in this car without any problems and I get 19 mpg, then I switch to Premium and mileage jumps up to 22 mpg, thats a big difference. I've done this test many times and I always get the same results.
That's quite possible in a high compression motor like the Crossfire's. If you run low octane fuel in your xfire, you'll probably experience pre-ignition, which means the fuel ignites and starts burning before it enters the combustion chamber. Therefore, you're not getting all the possible power out of the fuel that's being burned.
In a lower compression motor (read: normal everyday car whose manual says to use at least 87 octane fuel), higher octane fuel is going to have no effect whatsoever - except on your wallet.
What it amounts to is: put the kind of fuel in it that the manual says to, no matter what vehicle you're driving.
Other notes to those wishing to improve mileage: Check your tire pressure frequently. Underinflated tires can have a serious effect on mileage. Also, check your air filters and clean/replace them when they're dirty - Air/fuel mixture being off can have an effect on mileage.