Common Causes for Smoking Vehicles or Visible Exhaust

Engine Type	Visible Sign	Diagnosis	Possible Causes
Gasoline	Black or Gray Smoke	Smoke may be coming from incomplete fuel combustion	Clogged air filter Carburetor, choke, fuel injection or emission system malfunction Ignition timing off Blocked manifold Oil leaking on exhaust system
	Blue Smoke	Engine oil being burned	Oil leaking into combustion chamber Worn piston rings, valves or cylinders
	White Smoke	Coolant and/or water being vaporized in combustion chamber	Engine too cold (no repair needed) Head gasket leaking Cracked block or cylinder head
Diesel	Black or Gray Smoke	Smoke may be coming from incomplete fuel combustion	Faulty injection system Clogged air filter Wrong grade of fuel Timing may need to be adjusted Engine overheating Oil Leaking on exhaust system
	Blue Smoke	Engine oil being burned or atomized	Engine oil level too high Worn piston rings, valves or cylinders
	White Smoke	Fuel is not burning	Engine too cold (no repair needed) Faulty injection system Incorrect timing Engine overheating