well i road tested them and under ideal conditions from Tonopah Nv to Beatty Nv (95mi) it took 1.9 gal which was 50 mpg. then on the 2nd leg i went from Ridgecrest Ca up over Walker pass and then back to Beatty Nv (196mi of very mountainous roads) and took 4.6 gal which was 42.6 mpg. before the change this was much lower mpg of approx 38 low and 44 high. no power loss noticed at all.