Frost Stay Cool gives improved heat transfer, making a faster warm up and better cooling - up to 15 deg. C reduction in engine operating temperature. Stay Cool also contains a powerful anti-corrosion agent, very important with aluminium, steel, cast iron and bronze engine metal mixes, should be used in all engines. It does not contain damaging Ethylene Glycol but can be combined with antifreeze. A bottle of Stay Cool treats 30 litres of coolant. One of the contributing factors to overheating is using a high percentage of anti-freezes; this inhibits the effectiveness of the coolants heat transfer abilities. It is recommended that only a 25% fresh antifreeze solution is used with the 3% Stay Cool solution, this will ensure that there is a better heat transference and effective corrosion inhibition. For maximum protection, we would recommend that the coolant needs to be changed each Autumn in an older car but in a modern car it could be left for two or three years. See the How Do I Use Frost Stay Cool? article in the Technical Articles section See the How Do I Flush and Refill My Cooling System? article in the Technical Articles section.