Usually, the smoke that gets emitted is black, white, grey, and blue. The exhaust gases are an old-school way to detect symptoms of problems. The real issue is with cars that have been poorly maintained.

However, note that the smoke can be caused by different things depending on whether your car has a petrol or diesel engine.

The following are the types of car exhaust smoke and the cause of it:

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. It could also be due to a cracked cylinder or engine block.

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 gray 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. 

If you do not see smoke coming from the engine, pull over immediately and consider turning the engine off, as it could be a serious mechanical issue.

In general ensure that your car is well maintained and you regularly take it to a service facility for check-up.