Ask the Expert: What can exhaust smoke tell me?

June 7, 2019
Blue or gray, white, and black smoke all are indicators of different potential issues with your vehicle.

Question: What can exhaust smoke tell me?

Answer:

Blue or gray smoke typically means you are burning oil. Leaking oil into the combustion chamber, for example, could be caused by stuck rings from stiction, broken piston lands, worn out or broken rings, worn out cylinder bores or worn out valves, valve guides, valve seals, PCV valve, injectors, turbo seals, or the turbo itself.

White smoke can signify a few issues. Small amounts of white smoke can mean condensation in your exhaust system or inside of the engine. A small amount of white smoke can also mean unburnt fuel. Sticking injectors, faulty glow plugs, cold starts, low compression, injector timing, or a clogged air filter could be the cause. Excessive white smoke is almost always an indication of a water leak either by a cracked head, cracked block, or a blown head gasket.

Black smoke is due to an excessive amount of fuel. Diesel tuners can add more fuel to make you “roll coal”, but if you aren’t set up with a performance tune, the excess fuel can be from faulty or dirty injectors or from a lack of air due to a malfunctioning turbocharger or boost leak. You may also experience black smoke from low compression, poor fuel quality, and excessive carbon build up.

Information provided by Lubrication Specialties, Inc.

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