Car burning oil: how to tell and what it means
An engine should not use a meaningful amount of oil between changes, so a level that keeps dropping is worth investigating. The oil is either leaking out, which leaves spots or stains, or being burned inside the engine, which shows as blue exhaust smoke.
Can you keep driving?
Yes, as long as you keep the level up and have it checked soon. If the oil pressure light comes on, stop.
What a dropping oil level means
Oil does more than lubricate: it also carries heat away from the fast-moving parts inside the engine. When the level drops between changes, the oil is going one of two ways.
Either it is escaping from the outside of the engine, where it leaves a visible leak, or it is getting into the combustion chamber and being burned along with the fuel, where it leaves as blue smoke. That is why you look in two completely different places.
Common causes
- An external oil leak, seen as spots or stains under the engine
- Oil being burned in the combustion chamber, seen as blue exhaust smoke
What to do now
- Check the level properly: engine off and cold, car on level ground.
- Check it once a month, so you can see whether the level is actually dropping between changes.
- Look for fluid leaks under the engine bay and where the car is parked.
- Note the color of any exhaust smoke, and when it appears.
- Top up with the oil grade your owner's manual specifies.
- Book a check, and bring your notes on level, leaks and smoke.
Leaking out, or burning inside?
- Spots or stains under the engine, no smoke: an external leak.
- Blue exhaust smoke: oil being burned in the combustion chamber.
- Blue smoke with power loss or a rough idle: a cylinder may not be sealing properly, and a compression test checks each one.
- White smoke that persists after warmup: coolant, not oil, and urgent.
- Black exhaust smoke: the engine running rich on fuel, not burning oil.
What people often get wrong
That oil only needs checking at scheduled changes. A level that drops between changes usually points to a problem worth investigating, and you only notice it if you check.
When the car must go to a workshop
Blue smoke or a dropping level: get it checked soon. White smoke that persists after warmup: get it checked urgently. The oil pressure light on: pull over, turn the engine off, and tow it if the light stays on after topping up.
Read next
- Oil pressure warning light: stop the car now
- Engine misfiring: rough running and what it means
- Service light on: is something actually wrong?
- How to check your engine oil, and what the dipstick tells you
This page is general information and does not replace a professional assessment. Symbols, codes and behaviour vary between makes. Always check the handbook for your own car.
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