What can cause blue smoke from exhaust?

Answer 1

Blue smoke observed out the tailpipe most likely indicates that excess oil is being consumed in the combustion chambers (cylinders) of the engine. Being a GM tech over my 40 years I've seen excess oil consumption caused by excessive internal component wear (cylinder walls, piston rings, valve guides, etc) but also seen many cases where the oil is overfilled or there was sludge (blockage) in the area of the cylinder heads that prevented oil from being returned to the oil sump or a malfunctioning PVC system. Also, in many makes and models where a transmission incorporated a vacuum modulator by design, IF the modulator diaphragms ruptured it could permit Transmission Fluid to be drawn into the intake, hence lots of blue smoke. This was also true on earlier years that utilized a dual-action fuel pump that assisted vacuum for windshield wipers but has not been used for past 30 + years.So it is important to determine how severe the blue smoke is, how much engine oil is being consumed, and why, AND IS it really oil or is it TRANSMISSION fluid? before I would consider any major repairs. Also, remember to make sure that you do have clean, quality motor oil (and not a 0-W-20 unless you're on the North Pole) in the engine and the engine's PCV system is functioning as designed.