Thin white vapour on a cold morning
Normal condensation that disappears once the engine warms up.
Thick white smoke that does not clear
Can mean coolant is getting into the engine, for example from a head gasket fault. Check the coolant level when cold and watch the temperature gauge.
Blue or grey smoke
Usually oil burning, from worn rings, valve stem seals or a turbo seal. Check the oil level and how much it uses between services.
Black smoke
Too much fuel or not enough air. On diesels this can be injectors, a turbo or boost leak, an EGR fault or a blocked air filter.
What to tell the mechanic
The colour, when it happens (start-up, accelerating, all the time), any smell, oil or coolant use, and warning lights.
Safe to drive?
Thick white smoke with rising temperature or falling coolant: stop driving. Blue or black smoke without warning lights: book in soon and keep an eye on oil and coolant levels.
General guidance only, not a diagnosis. If in doubt, do not drive it and have it inspected. In an emergency, call 111.
Who can help
Get quotes for car repairs near you
Questions
Is some smoke normal on a diesel?
A small puff under hard acceleration on an older diesel can be normal. Constant black smoke is not, and it can also fail a WOF.
What should I put in the job?
Smoke colour, when it appears, and oil or coolant top-ups you have needed.