1. Black Smoke
Black smoke indicates that the engine is burning too much fuel, a condition known as running rich. This can be caused by several factors that disrupt the air-fuel mixture.
2. White Smoke
It usually means that coolant is being burned in the engine, which means that something is drastically wrong. The most common cause of this is a blown head gasket, which can quickly lead to an overheating engine.
3. Blue Smoke
Blue smoke is a clear sign that your engine is burning oil. The liquid can leak into the combustion chamber where it is burned along with fuel. You'll probably notice your car misfiring when you turn the keys in your ignition, or find your vehicle shakes more than usual when idle.
4. Grey Smoke
If the smoke from the exhaust pipe is either grey or bluish-tinged, it generally means that your engine is burning oil inside the combustion chamber. Burning oil could be due to many causes, from leaky valve seals to bad piston rings.