Blue or blue-gray smoke from the tailpipe means oil is reaching the combustion chamber and being burned along with fuel. The amount of smoke and when you see it tells you whether it is a cheap fix or major engine work.
You can drive a car that burns a little oil indefinitely if you keep checking the level. The risk is running out of oil between checks. If you are losing more than a quart per 1,000 miles, get it diagnosed and check the level weekly.
These small rubber seals keep oil from leaking down the valve stems into the cylinders. When they harden with age, oil drips into the cylinder while the engine is off. You will see a puff of blue smoke at startup that clears after a few minutes.
Get a free vehicle-specific diagnosis →Piston rings seal the cylinder against the wall. When they wear, oil from below sneaks up into the combustion chamber. Smoke is heavier under load (going uphill, hard acceleration) and gets worse over time. Major repair.
Get a free vehicle-specific diagnosis →A stuck-open PCV valve sucks oil out of the crankcase and into the intake. Cheap and easy to fix - usually $20-$50 for the valve, 15 minutes to swap. Always check this first before assuming worse.
Get a free vehicle-specific diagnosis →On turbo engines, oil-lubricated turbo bearings can leak past the seals into the intake or exhaust. You will see blue smoke under boost and may hear whistling or whining from the turbo.
Get a free vehicle-specific diagnosis →Blue smoke can mean a $20 PCV valve or $3,000 of engine work. Tell us when the smoke shows up and we will tell you which.
Get a free vehicle-specific diagnosis →Takes under a minute. Tell us your year/make/model and what you're seeing.
Oil-burning engines do not always throw codes, but these are the codes most commonly seen alongside blue smoke.
Yes - if you religiously check the oil level. The danger is running the engine dry between checks. Set a reminder to check oil weekly. If you are adding more than a quart per 1,000 miles, plan for a real fix.
Almost always failing valve seals. While the engine sits overnight, oil seeps past the worn seals into the cylinders. When you start up, that pooled oil burns off in a puff of blue smoke that clears within a minute.
Yes - and it is the cheapest cause. A stuck-open PCV pulls oil from the crankcase into the intake manifold, where it gets burned. Always replace the PCV valve before assuming worse - $20 fix, 15-minute job.
Most modern engines should use less than a quart per 3,000-5,000 miles. A quart per 1,000 miles is borderline. Half a quart per 500 miles or more is significant oil burning that needs attention.