Why Your Coolant Matters More Than You Think

Most of us don't think about coolant until the temperature gauge starts creeping toward red. By then, it's usually too late for a quick fix. The good news is that checking it takes about five minutes and needs nothing more than a glance under the hood.

Coolant, or antifreeze, runs through your engine and carries heat away so the engine stays at a steady temperature. If you let it run low or get dirty, the engine can overheat, and that's the kind of repair that gets expensive fast.

Checking the Level

Only do this when the engine is cold. I usually check mine first thing in the morning. Opening the cap on a hot engine is a bad idea, because the system is under pressure and the coolant can spray out and burn you badly.

Find the coolant reservoir, which is usually a semi-transparent plastic tank near the radiator. It has MIN and MAX (or LOW and FULL) lines on the side. The level should sit between them. If it's below MIN, add coolant, but use the type your owner's manual calls for. Mixing types or adding plain water can cause corrosion. Water is fine as a short-term emergency, but it dilutes the mix, so get it properly topped up soon after.

Reading the Fluid

Coolant comes in green, orange, pink, and blue, and the color won't tell you exactly what it is. What matters is whether it looks clean. Fresh coolant is bright and clear. If yours looks muddy, rusty, or cloudy, or if there's debris floating in it, the system is probably contaminated.

An oily film on top or a milky, mayonnaise-like look is more serious. That can point to a failing head gasket, so take the car to a mechanic soon rather than waiting.

How Often to Replace It

Coolant doesn't really run out. Its anti-corrosion additives wear down over time, and eventually the whole system needs a flush and refill. Topping up now and then is normal, but a full replacement is a different job.

Your owner's manual has the exact schedule, since it depends on the car and the coolant type. Many drivers go by roughly every five years or 100,000 km. Leave the flush to a mechanic unless you have the tools and experience to do it safely.