Exhaust Smoke Colours and What They Mean

Smoke from the exhaust is a clue. Its colour points to the likely fault.

Chart of exhaust smoke colours and their causes

Black smoke

Too much fuel is burning (rich mixture). Common causes are a dirty air filter, leaking injectors or faulty sensors. You may notice poor fuel economy.

Blue smoke

Engine oil is burning, often from worn piston rings or valve seals. You will use more oil than normal. Check the oil level often.

White smoke

Thick white smoke that does not clear, with a sweet smell, can mean coolant is entering the engine, often from a damaged head gasket. Check for falling coolant level and milky oil. Thin white vapour on a cold morning is normal condensation.

Grey smoke

Often linked to a clogged PCV valve, but it can also come from automatic gearbox oil being sucked in or other faults. Have it checked.

⚠️ Safety: If smoke comes with overheating, loss of power or warning lights, stop driving and get a diagnosis.

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