Antifreeze Coolant Mix Ratio Guide
Antifreeze (ethylene glycol) prevents your coolant from freezing in winter and raises the boiling point to prevent summer overheating. Getting the mix ratio right is essential — too little protection leads to freeze damage, while too much antifreeze actually reduces performance.
Freeze Protection by Mix Ratio
| Antifreeze % | Freeze Protection | Suitable For |
|---|---|---|
| 30% | 1°F (-17°C) | Mild winter climates |
| 40% | -17°F (-27°C) | Most of the US south |
| 50% | -34°F (-37°C) | Standard US recommendation |
| 60% | -62°F (-52°C) | Northern US, Canada, severe cold |
When to Replace Coolant
Standard green antifreeze should be replaced every 2 years or 30,000 miles. Extended-life (OAT/HOAT) coolants last 5 years or 150,000 miles. Coolant becomes acidic over time, corroding the cooling system from the inside out. Replace if it looks brown, rusty, or oily.
Frequently Asked Questions
Check your owner's manual under "Specifications" or "Fluids." Most passenger cars hold 6–12 quarts (5.7–11.4L). Trucks and SUVs typically hold more. You can also check online by entering your year, make, and model.
Always use distilled water. Tap water contains minerals that can form scale deposits inside the cooling system over time, reducing heat transfer and potentially clogging small passages.
Use an antifreeze tester — either a float-ball type or a refractometer. Add a few drops of coolant and read the freeze protection level. Refractometers are more accurate and cost around $10–$15.