For some modern vehicles, it is recommended to change the engine coolant every 5 years or 150,000 miles. For others, changing the coolant can be every 24,000 to 36,000 miles under severe conditions such as frequent towing or delivery service.
Coolant can deteriorate over time becoming more acidic and losing its rust-inhibiting properties, causing corrosion. This corrosion can eat away the heater core, radiator and any other aluminum parts in the cooling system. Vehicles with more than 60,000 miles the coolant should be tested periodically to prevent damage to radiator, water pump, thermostat and other coolant system components.