Whenever a fluid is in contact with metal, electrochemical degradation takes place which results in a higher then normal level of acid present in any given fluid. This higher acid level, if left unchanged, can result in very costly repairs. As a result, it is recommended to flush your cooling system, and most importantly, pH balance your antifreeze at least every 2 years or 30,000 miles. This will help reduce the acid level and extend the life of your radiator, heater core, water pump, head gaskets, freeze plugs, and heater hoses.