A common question asked in regards to vehicle diagnostics for repair is what a “smoking exhaust” means. In general, there are four “colors” of smoke coming from a vehicle’s exhaust that indicate a problem.
Common questions regarding exhaust smoking in our Ask a Mechanic forums are usually similar to this one posted by Sox:
Why does my Jeep run rough and blow black soot out of the tailpipe?
Typically, a well-tuned and running gasoline vehicle will have little or no discernible color to its exhaust – in other words, it will be nearly clear. Color to the smoke indicates a problem.
While the problem could be caused by many things, some general assumptions can be made from the color of the smoke being issued.