Car exhaust smoke explained

The colour and density of your exhaust smoke, can tell you a lot about your car and can act as an early warning to a fault developing.

White Smoke

Thin white smoke is usually nothing to worry about, most of the time you will see this on a cold morning, as its just condensation, when the engine gets hot, the thin white smoke will decrease, or completely disappear.

Thick White Smoke, can be a lot more concerning. This type of smoke can indicate a serious issue and should be looked at immediately. This type of smoke can indicate the following, blown Head Gasket, engine over heating, cracked engine block. Any of those three can cost or cause an expensive repair bill and you should stop driving immediately.


Black Smoke, this smoke is not as alarming as thick white smoke, but still needs to be looked at soon before a fault develops. This type of smoke, usually indicatedsthe following, faulty sensors, faulty injectors, faulty fuel regulator or a clogged DPF filter (diesel cars only)

Grey Smoke, again this is not to alarming, but can indicated a serious issue. Grey smoke could mean the following, faulty turbo (you should notice power loss), bad transmission fluid, faulty transmission vacuum module. You should get this investigated soon, before it gets worse and a fault develops.


Blue Smoke, is quite alarming and it usually means one thing, there is an oil issue. Blue smoke is usually caused by the following, oil leak in the combustion chamber, burning to much oil, valve seals or piston rings are worn. Again get this looked at soon, because this could lead to a major fault.



Another way to determine if the exhaust smoke is bad, is the smell of it.

Sweet smell, antifreeze which is used in coolant has a sweet smell, so if the smoke smells sweet, that usually indicates a coolant issue.
Coolant issues normally mean
• Blown head gasket
• Engine over heating
• Cracked engine block

Oil smell, if the exhaust smoke smell like oil, this will usually indicate an oil issue.
• Oli leak in the combustion chamber
• Oil and water are mixing together
• The engine is burning excessive oil

If your exhaust makes any of these, other than thin white smoke, it is vital to get it checked by a mechanic. Getting you car looked at, when the smoke starts, could stop a major fault from happening.