Blue or white smoke from my car exhaust – what does it mean?

March 02, 2018 by

It’s easy to assume that because your car is working then there’s nothing to worry about. But if you notice any coloured smoke coming out of the exhaust then it could be a hint that a mechanical problem could be waiting in the wings.

The colour of the smoke that comes out of your car’s can mean different things, and is an indication of what might be wrong. Read on for details that might be worth looking out for.


Vapour looks like white smoke but is usually a lot less thick. Generally it’s nothing to worry about, and tends to mean that the engine hasn’t warmed up yet – or that it’s cold outside! Most cars show that the engine is warmed up by a temperature gauge near the speedometer and, if everything’s ok, it should be around the halfway mark. To ensure everything is fine, wait until the engine is warm enough and then check your exhaust again. If it’s still producing smoke, it might be worth checking out.

Black or grey smoke

Any smoke that comes out of your exhaust means that you need to get a garage to check over your car, as it can be unhealthy for your engine or the environment – or both. Black or grey smoke usually means that the engine isn’t running as healthily as it should be, but the associated problems shouldn’t be too time-consuming or expensive to fix.

It can be a range of problems, but the most common ones include a malfunction in the fuel injection system, a clogged air filter, the engine timing being out of sync or a blocked manifold. Once fixed, your car should be back to full health – providing there are no other underlying problems. For diesel cars all of the above apply, but it could also be a sign that the engine is running a bit too hot and overheating, or your diesel particular filter is automatically burning off soot, which is normal once in a while.

Blue smoke

Blue smoke from a car exhaust is generally a bad sign, and the cause of it will need to be repaired as soon as possible. It’s either a problem to do with the oil, or internal engine components. In petrol cars, it might suggest that oil is leaking into the engine block where the fuel is mixed with air, while in diesel cars it may simply suggest that there is too much oil in the engine. In the worst cases, the cylinder heads, pistons or valves might all be worn down. Regardless, you’ll want to get your car looked at by a reputable garage if it’s emitting blue smoke.

White smoke

White smoke also needs to be checked immediately, because it can be a sign that your engine is on its last legs. For diesel cars it can mean that the engine timing isn’t right, that there’s a fault in your fuel injection system, or that the engine is overheating. And if you drive a petrol car and see white smoke, it’s really not good news. It could be that either the cylinder block or head are cracked, or that the head gasket is leaking. If the head gasket is not fixed immediately, it can spell the death of that engine. In some cases the cost to fix this problem is more than the car is worth.

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