Ethanol-blended fuel acts as a solvent, and it has the unattractive characteristic of being water absorbent. After only a brief time it can experience phase separation, where the ethanol attaches itself to water molecules, dropping to the bottom of the tank in an ethanol-water cocktail. K100 Fuel Treatment prevents this phase separation, eliminating water and water related problems. It also acts as a fuel stabilizer, keeping fuel fresh for up to two years, and it adds lost lubricity to winter blends. 1 ounce treats 2 gallons. $12 (8 ounces) and up.