George, Excellent reply and I appreciate the time to write the statement. B12 Chemtool or what I call Berryman B12 is Toluene in a concentrated form which as you know will hasten the process of dissolving or cleaning the tank. Everyone is naturally correct that the cars need to be driven, but since most of them aren't our daily drivers we have to contend to what goes on. I don't use the chemical that much, unless I feel I'm possibility getting a little sluggish and maybe this mechanic in the bottle will help a little. But I feel the main thing is if you put it in the tank just to make you feel like your doing something good, then drive it out and don't leave high concentrates there. We have about 8 O rings in the fuel distributor and some chemicals may make them swell. Just be careful. John Hervey