How long is coolant supposed to last in your car?

It depends on the vehicle and the coolant, the average time between flushes is 12 months or 30,000 miles/48280 kilometers for silicated coolants and up to five years or 100,000 miles/160934 km for an extended drain coolant. You can tell which type of coolant you have by the color. Over time, dirt and other contaminants can build up in the fluid, or it may become acidic. When this occurs, the radiator fluid is much less effective and should be changed.