I'm getting over 1mpg improvement and drive much faster than usual. Took a small trip and saw 18mpg with the cruise set at 85, few blips to 100. I got 12/16 stock and feel I could net 15/20 if I stopped driving fast. Too bad this thing sounds awesome running through 3rd wide open or I'd save some money, it'll probably get worse once I get the blower. Highly recommended mod for $300.