Wynns Extreme Cooling System Degreaser is designed to effectively remove oil and sludge from your vehicle's cooling system, which can be caused by leaks from a heat exchanger or cylinder head gasket. This degreaser cleans the entire cooling system, keeping residues in suspension during the cleaning process. It helps restore heat transfer and ensures the optimal operation of cooling system controls. Suitable for petrol, hybrid petrol, diesel, and hybrid diesel engines, and compatible with all water-cooled systems. To use, add one bottle to the cooling system, treating up to 7 liters of coolant. Use as needed. Add directly into the radiator or expansion tank. Warm up the engine with the heater on HOT, and let it idle.