Coolant Mix Calculator
Calculate the exact antifreeze-to-water ratio for your target freeze protection, or find out how much to add when topping off.
Freeze & Boil Point Reference
| Mix Ratio (AF/Water) | Freeze Point | Boiling Point | Note |
|---|---|---|---|
| 100% / 0% | +3°F | 223°F | Worse than a mix! |
| 70% / 30% | -84°F | 235°F | Extreme climates |
| 60% / 40% | -62°F | 232°F | Cold climates |
| 50% / 50% | -34°F | 228°F | Most common |
| 40% / 60% | -12°F | 224°F | Mild climates |
| 30% / 70% | +2°F | 221°F | Not recommended |
Coolant Types Explained
IAT (Inorganic Additive Technology) is the traditional green coolant, typically rated for 2 years or 30,000 miles. OAT (Organic Acid Technology) is the orange or red Dex-Cool type, rated for 5 years or 150,000 miles. HOAT (Hybrid OAT) is pink or yellow and used by European and Asian manufacturers — often rated for 5 years as well. Always check your owner's manual before adding coolant.
Why 100% Antifreeze Is Not Better
Pure antifreeze (ethylene glycol) actually freezes at +3°F — far warmer than a 50/50 mix. It also transfers heat less efficiently than water. The optimal balance for most climates is 50/50, which provides freeze protection to -34°F and raises the boiling point to 228°F (with a pressurized cap).
Signs of Coolant Problems
Warning signs include a sweet smell from the engine bay, white smoke from the exhaust (coolant entering the combustion chamber), milky oil on the dipstick (coolant mixing with oil), or the temperature gauge running hot. A coolant leak usually presents as puddles of bright green, orange, or pink fluid under the vehicle.