Holy smoke! What does your exhaust smoke mean?

John Tucker

By: John Tucker

So, you’re driving along and suddenly you notice smoke coming out of your exhaust.

Not what you want to see, right?

You’re probably thinking of a trip to your nearest garage and costly car repairs, but that’s not necessarily the case.

We’ve all been there and it’s a worry, especially if you’ve kept your car regularly serviced.

But what does it mean?

Smoke coming from your exhaust can mean that something isn’t working properly, or that there’s some damage to your car’s engine or exhaust system.

The colour of the smoke can give you some idea of what could be wrong.

So, what does the colour of the smoke mean?

White smoke from your exhaust

If you’re seeing white exhaust smoke, it could mean two things, depending on how thick it is.

If the smoke is thin, it’s most likely to be steam rather than actual smoke and is caused by condensation in the exhaust system.

When you start your car, the warming engine turns the condensation into steam and the white smoke you see should disappear.

Nothing to worry about.

But what if the white smoke is thick?

white smoke from exhaust

Thick white smoke from your exhaust could be a sign of coolant in your car’s combustion chamber. This could be caused by a cracked cylinder head, a blown gasket, or it may just be a cracked seal.

Check your coolant level – is it low? If so, you probably have a leak.

You should have your car checked immediately at your nearest garage to have this problem fixed.

But you’re seeing black smoke, surely that can’t be good?

Possibly not, but it’s often a simple fix…

Black smoke from your exhaust

Nobody wants to see black smoke billowing from their exhaust. It can be shocking to see and surely the sign that something catastrophic has happened to your car.

Hold that thought.

Black exhaust smoke simply means that your engine is burning too much fuel.

Engines need both fuel to burn and oxygen to burn it with. If there’s too much fuel in the combustion chamber and not enough oxygen to burn it with, it can cause black smoke to come from your exhaust.

If you see black smoke, it could be a sign of a problem with your air filter, fuel injector or EGR valve if you drive a diesel.

These can be quick, inexpensive fixes, but you should have this checked at your local garage. All good so far, not too much to worry about.

Blue smoke from your exhaust

If you’re seeing blue smoke coming from your exhaust, it is likely to be caused by oil leaking into the combustion chamber and being burned with the fuel.

Surely that’s bad, right?

Not necessarily.

blue smoke from exhaust

If your car is old, or has covered a large number of miles, it’s fairly common for engine seals to wear and allow oil to leak into the combustion chamber.

Sounds expensive to fix.

Not in all cases.

If your car is old you can manage this problem by regularly checking your oil level and topping up when it gets a little low.

But what if your car is new?

If you’re seeing blue smoke coming from your engine and your car is fairly new, you’re going to want to have this checked by your local garage.

It could be a sign of a more serious issue that, if left, could result in an expensive repair bill.

What sort of serious issues?

Burning oil can cause damage to spark plugs. If left, the spark plugs could fail entirely causing poor fuel economy, engine misfires and difficulty starting your car.

Allowing fuel to mix with the oil in your engine’s crankcase can reduce the efficiency of the oil in protecting your car’s engine. This can cause serious issues, possibly leading to expensive engine repair.

Finally, blue smoke can be a sign that your turbocharger isn’t working correctly. If you’ve noticed a loss of power, it’s possible that oil is getting into the intake.

In these cases, you should have a mechanic look at your car for you.

A final note.

If you think you can see grey smoke coming from your exhaust, treat it in the same way as blue smoke. It’s probably caused by your car burning oil or a problem with your turbo (if you have one).

So what should you do?

It’s simple.

Most of these issues can be fixed by taking your car to be checked at your local garage. Generally, they are simple fixes that a qualified technician will be able to diagnose and repair without much fuss.

What you shouldn’t do is ignore the signs. Even if you don’t have any warning lights on your dashboard, smoke coming from your exhaust is a sign that something isn’t right.

Be smart, get it checked.

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