I'm averaging 14 mpg with my 1997 Mach 1. Last year I would average about 9-10 mpg. Only thing I did different this year is add the Fitch Fuel Catalyst drop-ins in my tank. I am also running 89 octane instead of the required 91 that Doo calls for in my sled. I figure that the 10 cents a gallon I am saving more than pays for the FFC, plus I get better mileage.