Car coolant, also known as antifreeze, is a liquid that circulates through your engine to regulate its temperature. Its primary job is to absorb excess heat from the engine block and transfer it to the radiator, where it's dissipated into the air. This prevents the engine from overheating in summer and freezing in winter. Modern coolants also contain additives that protect against corrosion and scale buildup within the cooling system. The most common type is an ethylene glycol or propylene glycol mixture, typically pre-mixed 50/50 with distilled water.
The cooling system is a sealed loop. A water pump pushes the coolant through passages in the engine (called water jackets), where it heats up. The hot coolant then flows to the radiator at the front of the car. As air passes through the radiator fins, the coolant cools down before cycling back to the engine to repeat the process. A thermostat valve regulates the flow to ensure the engine reaches its optimal operating temperature quickly and stays there.
Using the correct coolant is critical. Different manufacturers require specific formulations with unique additive packages (technically known as inhibitor technology) to protect the metals and plastics in their engines. Using the wrong type can lead to premature corrosion, pump seal failure, and costly damage.
| Coolant Type (by color & technology) | Common Vehicle Manufacturers | Key Feature / Protection | Typical Service Interval (Miles/Years) |
|---|
| IAT (Inorganic Additive Technology) | Older GM, Ford, Chrysler | Silicate & phosphate-based for fast-acting protection | 30,000 miles / 2 years |
| OAT (Organic Acid Technology) | General Motors (Dex-Cool) | Long-life, nitrate-free, protects aluminum | 150,000 miles / 5 years |
| HOAT (Hybrid Organic Acid Technology) | Ford, Chrysler, European brands | Combines OAT and silicate for broad protection | 100,000 miles / 5 years |
| Si-OAT (Silicated HOAT) | BMW, Mercedes-Benz, Volvo | Enhanced aluminum protection with silicate | 150,000 miles / 5 years |
| P-HOAT (Phosphated HOAT) | Hyundai, Kia, Japanese brands | Phosphate-based, optimized for Asian engines | 100,000 miles / 5 years |
You should check your coolant level regularly via the translucent overflow reservoir when the engine is cool. If it's low, top it up with the correct pre-mixed coolant specified in your owner's manual. A professional coolant flush and replacement at the recommended interval is one of the most cost-effective ways to ensure your engine's longevity.
