The color of vehicle exhaust can tell us a lot about vehicles. You can even predict the problem in you vehicle by looking at smoke color. Generally the smoke emitted by the vehicles is colourless. But in case of problem the smoke colours may vary. The commonly observed colours are black, white or blue etc. The smoke colour may change due to burning of other materials i.e. lubricant, water, coolant etc along with petrol Let’s see what does a particular exhaust color means. Smoke Color:Blue/gray
It is the most commonly seen exhaust color. You might notice block smoke at the time you pull your choke, but this is normal. Black exhaust smoke appears when the vehicle burns very fuel rich mixture. The Ideal Air-fuel ratio for Gasoline is 14.7:1. This is also called stoichiometric Air-Fuel ratio. Any mixture containing fuel more than the stoitiometric one is called rich mixture. The reasons for mixture to get rich may be :
All these can choke the air supply to the engine causing the Air-fuel mixture to be rich and produce black smoke on burning.
Smoke Color: Thick white/gray
The white smoke may be caused due to water vapor. It means that some water is present inside and is coming out as vapor. This occurs only at the starting of vehicle and stops after some times. But a steady stream of thick white/gray exhaust smoke coming from your muffler could mean there is a damaged head gasket. In this case the coolant may be leaking and burning inside combustion chamber. A coolant leak in the summer could easily lead to an overheated engine.
Heavy white/gray exhaust smoke could also mean a cracked block or cylinder head—both very serious problems that should be addressed quickly.