Blue smoke from the exhaust
The buyer question: "blue smoke from exhaust"
Arrange an inspection promptly. Stop if smoke becomes heavy, oil pressure is low, the engine runs poorly, the temperature rises, or oil is leaking onto a hot component.
What could cause it
More than one problem can cause the same symptom. These are places to inspect, not a diagnosis.
- Oil entering the combustion chamber
- A turbocharger or crankcase ventilation issue where fitted
- Worn seals, rings, or other engine conditions
- Oil leaking externally and reaching hot exhaust parts
Safe things to check
Keep clear of moving parts, hot components, and traffic. Use the owner's manual for vehicle-specific instructions.
- Note whether smoke appears at startup, acceleration, or after deceleration
- Check oil level only as described in the owner's manual
- Look for external oil spots or burning odor without touching hot components
Stop if the oil pressure warning, heavy smoke, a strong burning odor, or a rapid oil-level drop appears. Arrange professional help instead of driving until the oil is gone.
What a mechanic may check
A mechanic may inspect for external leaks, check oil consumption, scan the engine, inspect crankcase ventilation and turbo systems, and run compression or leak tests where appropriate.
If you are considering this car
Document blue smoke from a cold start and under different driving conditions. Ask for oil-consumption records and an independent engine inspection.
Questions for the seller
- When does the smoke appear, and how often does the vehicle need oil?
- Has the engine, turbo, ventilation system, or exhaust been repaired?
- Can I see oil-change records and a written inspection?