Do you mind if I smoke?

You're stopped at a light. The car in front of you has smoke coming out their tailpipe. Worse: you're looking to buy a used car, and smoke comes out of that tailpipe. Or even worse: smoke starts coming out of your tailpipe. What does it mean?

Exhause smoke can be black, blue, or white/gray-ish. It means something is wrong with the engine.

Black smoke means that the engine is burning too much oil. It can be simply that the air filter is clogged. Just change the air filter. If you go to change the filter, and it's soaked with oil, then that's a problem.

Other causes of Black smoke are faulty fuel injectors, a bad oxygen sensor, or a blocked intake manifold.

Blue smoke indicates that the engine is burning too much oil. This can be caused by worn engine componets: bad valve seals, bad piston rings or a bad PCV valve.

Blue smoke can also be due to too much oil in the engine. This can be the result of an owner misreading the dip stick and putting too much oil in, or from going to one of these fast oil change places, who just take anyone off the street, put a uniform on them, and say go. If your car has too much oil in it, then severe damage could occur.

 White or gray smoke is very bad. It indicates that coolant is somehow getting in the combustion chambers. This can be caused by a cracked cylinder head, cracked engine block, or a blown head gasket.

What to do? If it's coming from the car in front of you, then say a prayer for them. If you're looking to buy a used car and it's smoking, walk away, no matter what excuses the seller comes up with.

What if the smoke is coming from your car? First, stop driving it and have it towed to your trusted garage. Second, don't panick. Engines can be repaired, rebuilt or remanufactured. A good automotive machine shop can seal cylinder heads & engine blocks, depending on the severity of the damage.

These repairs are expensive. Rule of thumb: If the repair is more than half of what your vehicle is worth, then trade the car in for another one. It's not worth fixing in that case.

One thing, and I say again: If your car starts to smoke, then pull over and call for a tow. Too many times I saw problems that aren't too bad, still driven making the damage worse. The cost of the repair will go up astronomically.

Thank you for reading. If you like it, then please share. Feel free to ask questions or make a comment.