Radiator Coolants is a tinted liquid that you put (along with water) in your radiator to help regulate engine temperature. It also helps prevent the water in your radiator from freezing, boiling, or evaporating. Along with fuel and oil, antifreeze is essential to a properly functioning engine. Without it, the heat from combustion would cause the engine to rapidly overheat or even completely seize up. Radiator Coolants also lubricate cooling system components that contact water and keeps metal components from destruction or damage.