Short answer
Thin white vapor from the exhaust on a cold morning that fades after a few minutes is just condensation. Thick white smoke that smells sweet means the engine is burning coolant. Blue or gray smoke means it is burning oil. Black smoke means too much fuel. If the smoke is heavy or the temperature gauge climbs, pull over, turn the engine off and call a tow.
Safety first
If you see heavy smoke, smoke from under the hood or flames, pull over where it is safe, turn the engine off and get everyone out and away from the car and traffic. Then call 911. Do not open the hood if you see flames, and never open a hot radiator cap.
What the smoke from your exhaust means
1Smoke comes out of the exhaust
Look at how thick it is, notice any smell and see whether it goes away once the engine warms up. That tells you more than the color alone.
Read all the steps
- Smoke comes out of the exhaust. Look at how thick it is, notice any smell and see whether it goes away once the engine warms up. That tells you more than the color alone.
- Thin wisps on a cold day: normal. Thin white vapor that fades after a few minutes is water condensing in a cold exhaust. Nothing to fix.
- Thick white and sweet: coolant. Thick white smoke that keeps coming and smells sweet means coolant is burning inside the engine. Watch the temperature gauge and have it checked soon.
- Blue-gray: oil. Black: too much fuel. Blue-gray smoke means the engine burns oil: check the dipstick often. Black smoke means too much fuel, which wastes gas and can fail an emissions test.
- Heavy smoke or gauge rising? Pull over. Turn on your hazard lights, pull over safely and turn the engine off. Do not keep driving: call a tow or a mobile mechanic.
- Still not fixed? Call a mechanic Especially if: thick white smoke that does not clear once the engine warms up.
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What each kind of smoke usually means
- Thin white vapor on a cold morning, gone in minutes: condensation, normal.
- Thick white smoke with a sweet smell that does not clear: coolant leaking into the engine, often a head gasket. The coolant level keeps dropping.
- Blue or gray: oil getting burned, from worn seals, worn piston rings or a turbo seal. You end up adding oil between changes.
- Black: too much fuel, from a leaking injector, a bad sensor or a clogged filter on the engine’s air intake.
What not to do
- Do not keep driving with thick white smoke and a rising temperature gauge: the engine can be ruined.
- Do not let the oil run low if the car burns oil: check the dipstick every time you get gas.
- Do not pour in additives to hide the smoke: find the cause.
When to call a mechanic
- Thick white smoke that does not clear once the engine warms up.
- The coolant level keeps dropping with no leak under the car.
- Blue or gray smoke, or you add oil between oil changes.
- Black smoke, poor gas mileage or a check engine light.
- Smoke from under the hood (pull over and call right away).
Frequently asked questions
Is white smoke from the exhaust bad?
Thin white vapor on a cold morning that goes away in a few minutes is normal. Thick white smoke that keeps coming and smells sweet is not: it usually means coolant is burning in the engine.
What does blue smoke from the exhaust mean?
The engine is burning oil, usually from worn seals or piston rings, or a turbo seal. Check the oil level often and have it diagnosed.
What causes black smoke from the exhaust?
The engine gets too much fuel for the air it takes in. Common causes are a leaking fuel injector, a faulty sensor or a clogged intake filter.
Can I drive with smoke coming from the exhaust?
With thin vapor, yes. With heavy smoke or a temperature gauge that keeps climbing, no: pull over, turn the engine off and call a tow or a mobile mechanic.
Is white smoke always a blown head gasket?
No. Condensation also looks white. The warning signs are thick smoke that does not clear, a sweet smell and coolant that keeps disappearing.