I've used Seafoam in the past and I'm currently using Berryman's B-12 Chemtool. I use a quarter of a bottle every few fill ups. I'm not trying to clean a clogged fuel system, just trying to keep it clean. That said, the first time I used Berryman's B-12, I noticed an improvement in MPG by about 4mpg. I never saw an increase in mpg after using Seafoam.