Here are some general rules of thumb that apply to any car:
| Symptoms | Possible Cause | Fix |
| White smoke, acrid smell | Vaporised coolant | Probably from head gasket leak (usually fails at back of an I5 engine) -- replace head gasket (duh!) |
| Blue smoke on shifting, burnt oil smell | Valve stem oil seals | Find the right mechanic, and it's a surprisingly cheap job |
| Blue smoke on overrun w/o shifting, vaporised oil smell | More serious wear, perhaps rings | Very rare in Audis, common in Beemers |
| Grey or black smoke, just plain stinks | Seriously rich mixture | Adjust mixture (duh!) |
