Symptoms
- Bluish-gray smoke from the tailpipe
- Smoke often worse at startup or after coasting/idling then accelerating
- Oil level dropping faster than normal between changes
- Burning oil smell
Likely causes
- CommonWorn valve stem sealsOil seeps past worn seals into the cylinder, often causing smoke on startup or deceleration.
- CommonWorn piston ringsRings that no longer seal well let oil past into the combustion chamber, worse under load.
- PossibleFailing turbocharger sealsOn turbocharged engines, worn turbo seals let oil into the intake or exhaust side.
- PossibleClogged PCV valve or systemA stuck PCV system can pressurize the crankcase and push oil past seals.
What to do
- Note when the smoke happens: at startup, on deceleration, or under acceleration, since the pattern helps narrow down the cause.
- Check the oil level and note how much it's dropped since the last check.
- Have a shop perform a compression or leak-down test to check piston ring and valve condition.
- Check the PCV valve and hose for clogging as a simpler, cheaper first step.
- Have the turbocharger inspected for play or oil in the intake piping if the car is turbocharged.
- Plan for the appropriate repair (seals, rings, or turbo) based on test results, since this doesn't fix itself and gets worse over time.
Tools and parts
- Dipstick
- OBD-II code reader
PCV valveSearch: “PCV valve for [year make model]”
Valve stem sealsSearch: “valve stem seals for [year make model]”
When to call a pro
See a mechanic for a compression or leak-down test before committing to a repair, since the fix ranges from a cheap PCV valve to a major engine job.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.