Exhaust smoke - what the colour tells you

The colour of the smoke is the fastest way to narrow down what's actually wrong.

Possible causes

  • Blue smoke - the engine is burning oil, often worn piston rings or valve seals
  • White smoke (thick, constant) - coolant is entering the combustion chamber, often a head gasket
  • Black smoke - the engine is running rich, often a fuel system or sensor fault

A catalytic converter or lambda sensor fault can also trigger a check engine light alongside the smoke - worth checking both together.

Related parts

Catalytic converter and lambda sensorExhaust system