Coolant, also called antifreeze, controls engine temperature and protects against freezing, boiling, and corrosion. Modern long-life coolants last far longer than older green formulas, so match the interval to your fluid type.
| Coolant Type | Typical Interval | Cost |
|---|---|---|
| Green (IAT) | 2-3 yr / 30k mi | $100-$150 |
| Long-life (OAT) | 5 yr / 100k-150k mi | $100-$200 |
| HOAT (hybrid) | 5 yr / ~100k mi | $100-$200 |
Traditional green (IAT) coolant is usually changed every 2 to 3 years or about 30,000 miles. Long-life OAT and HOAT coolants (often orange, pink, blue, or yellow) commonly last 5 years or 100,000 to 150,000 miles.
Always use the coolant type and color specified for your vehicle; mixing incompatible chemistries can cause gelling and corrosion.
Over time the corrosion inhibitors deplete, and the coolant becomes acidic. Depleted coolant can corrode the radiator, water pump, and heater core even though it still prevents freezing.
Only check coolant when the engine is cold. Look for the correct level between the min and max marks and a clean color. Rusty, brown, or cloudy coolant should be flushed.
A cheap coolant tester or test strips can measure freeze protection and pH.
Topping off a low reservoir is fine short term, but a chronically low system points to a leak. A full flush replaces old fluid and removes buildup.
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