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 one gallon of Prep Fluid is recommended for all cars and motorcycles converting to NPG+ or NPG. Prep Fluid is NOT intended to be a stand-alone operating coolant, but as a flush only.