Actually, back before the 1970s, plumes of thick, foul smoke pouring from a car’s exhaust probably meant your ride was running just fine. But car-centric cities like Los Angeles were choking on the fumes, so automakers had to clean up their acts. Today, exhaust streams are so pristine that they’re often not even visible to the naked eye.
Unless, that is, something’s wrong with your car.
In other words, it’s often bad news whenever smoke clouds are pouring out of a modern exhaust system. But different colors mean different things, so the first troubleshooting step is to identify whether the smoke is white, black, or bluish gray.