Bill & Jon - Prist is used in Jet fuel to prevent icing of suspended water particles. Prist lowers the freezing point of suspended particles to minus 46 degrees as found in the upper atmosphere. It is not a product used for non-suspended water. Also Prist dropped the required testing and subsequent certification as a microbiostat (means kills microbes) in 1994. There is some evidence that is does, but the manufacturer no longer makes this claim. Good for jets....not much use in a coach.