Evans Prep Fluid is a waterless cooling system flush designed to seek out remaining water after draining the cooling system of an engine. Prep Fluid 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 Prep Fluid is recommended for heavy duty diesel engines and 1 gallon of Prep Fluid is recommended for all motorcycles and cars converting to NPG+ or NPG. Prep Fluid is NOT intended to be used as a stand-alone operating coolant, but as a flush only.