While Ford recommends using "Premium" grade fuel, some folks have had no problems using regular unleaded fuel with 87 octane, and saved a few bucks at the pump as well. On the other hand, some SHO owners have attempted to run fuel with lower octane which has resulted in the motor "pinging." Our suggestion, is that if you want to save some money by running a lower grade of fuel, go right ahead. If your car starts to "ping," then use the next higher grade of fuel until the "pinging" stops. Otherwise, there is no performance advantage to running higher octane fuel, unless you are running nitrous oxide.