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Blue Smoke From The Exhaust

Blue-grey smoke means the engine is burning oil, from worn valve stem seals, piston rings, the turbocharger or the crankcase ventilation.

High risk

Have it checked promptly and watch the oil level. Burning oil can damage the catalytic converter.

Short answer · What does blue smoke from the exhaust mean?

Blue or grey-blue smoke means oil is reaching the combustion chamber. A puff on start-up often points to valve stem seals; smoke under acceleration to piston rings or the turbo. Check the oil level often and have the cause found before the catalytic converter is damaged.

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Safe checks you can do

  1. Check the oil levelBurning oil lowers the level between services.
  2. Note when it smokesOn start-up, after idling, or under acceleration.
  3. Look at the spark plugsOily plugs show which cylinders burn oil.

Questions that narrow it down

  1. Only a puff at start-up?Valve stem seals are likely.
  2. Smoke under acceleration?Rings or turbo seals.
  3. Is it a turbo engine?Turbo seals can leak oil into the intake or exhaust.

Possible causes

Listed without ranking. Use the questions above to see which ones fit your car.

  1. Worn valve stem sealsSmoke after standing.
  2. Worn piston ringsSmoke under load.
  3. Turbocharger seal wearOil in intake or exhaust.
  4. Blocked crankcase ventilationPressure pushes oil into the intake.
  5. Overfilled oilExcess oil can be drawn in.

Questions about Blue Smoke From The Exhaust

Can I keep driving if I top up the oil?

For a while, if the smoke is light. Heavy oil burning damages the catalytic converter and can foul spark plugs.

Is blue smoke an inspection failure?

Visible smoke and high emissions often fail a roadworthiness test.