Car symptom
Blue smoke from the exhaust
Blue smoke is burning oil. When you see it tells you whether it is the valve seals, the rings or the turbo.
Most likely causes
- Valve stem seals (on start-up)
- Worn piston rings (under load)
- Turbo oil seals
- Clogged PCV system
Checks to run
- Note when the smoke appears
- Compression and leak-down test
- Check the PCV system and turbo
Tools you may need
Compression tester
Leak-down tester
Boroscope
Confirm before replacing. These are hypotheses to check — never buy parts on a guess. If the fault involves brakes, airbags or fuel under pressure, use a professional.
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FAQ
It depends on the cause. Some causes are cheap and quick; others (like a head gasket or seized caliper) need attention soon. Work through the checks in order and confirm before replacing parts.
Start with the free checks listed here. If they involve high voltage, fuel under pressure, airbags or brakes, let a professional handle it.
The interactive diagnostic asks targeted questions to narrow it down, and every cause must be confirmed with a measurement — never guess.