How Often to Change Engine Coolant
Reviewed by GarageDex editorial
GarageDex's data shows modern long-life (OAT/HOAT) coolant typically lasts about 5 years or 100,000 miles for the first change, then every 3 years or ~50,000 miles after that. Older green (IAT) coolant is shorter - roughly every 2 years or 30,000 miles. Always follow your owner's manual and use the coolant type your engine specifies; mixing types can cause gelling.
What affects the interval
- Coolant type - long-life OAT/HOAT lasts far longer than old green IAT.
- Heat & towing - sustained high temps age coolant faster.
- Topping up with the wrong type - shortens life and risks gelling.
When to change it
Go by the manual, but flush sooner if the coolant looks rusty or murky. Use the correct type and the right amount - look up your coolant capacity so you refill to spec.
Frequently asked
How often should coolant be changed?
Long-life coolant: about 5 years / 100,000 miles for the first change, then every ~3 years / 50,000 miles. Older green coolant: roughly every 2 years / 30,000 miles. Your owner's manual is the final word.
What happens if you never change coolant?
Old coolant loses its corrosion inhibitors and turns acidic, which can corrode the radiator, water pump, and heater core, and its freeze/boil protection degrades - risking overheating in summer and freezing in winter.
What are the signs coolant needs changing?
Rusty, brown, or murky coolant instead of clear green/orange/pink; visible sediment; a sweet smell; or the engine running hotter than normal. If it looks dirty, it's due for a flush.
Can I mix different coolant types?
Avoid it. Mixing incompatible coolants (e.g. green IAT with orange OAT) can form a gel that clogs the cooling system. If unsure, flush and refill with the single type your manual specifies.
Need your car's exact spec? Find your coolant capacity →