Will immediately seal small leaks caused by external damage, porous solder joints and hairline cracks in cooling systems of all water cooled engines. Coolant is prevented from entering the combustion chamber due to internal leaks from head gasket etc. It does not react with oxygen or heat and will never prevent system flow or cause overheating. Radiator Stop Leak works as long as it’s in the coolant. For any water based cooling system with or without filters. Safe to use with aluminum and plastic radiators. Contents (250 mL) is sufficient for 10 Liters (2.6 gal.) coolant. Compatible with most types of coolant or anti-freeze. May be used as a preventive.