An expert from The AA who helps stranded drivers at the roadside has explained what to do if you see different coloured smoke coming from your car's exhaust ... while black smoke signals excessive ...

a smoking exhaust often indicates a problem. Blue smoke typically suggests your car is burning oil, grey smoke may indicate oil burning, a faulty turbocharger, or fuel system issues, and black ...

But the smoke test means something else for cars, especially those powered by diesel ... in exhaust passing through the tube will scatter light in a predictable way, and the numbers work out ...