Evans Waterless Coolant Prep Fluid is a waterless flush designed to seek out the remaining water after draining the cooling system of an engine. It should be used when block drains are unavailable or cannot be removed. It is not a substitute for thoroughly draining the cooling system and related components. A minimum of 2 gallons of Evans Prep Fluid is recommended for automobiles, and it is recommended to fill the system for motorcycles converting to their High Performance coolant or Powersports coolant.