It sounds as if the rings to the pistons are worn. This allows a bit of oil to seep into the combustion chamber. Right now it might not be too bad since it burns off and disappears when the engine is warm. Sooner or later you're going to need a 'ring job'. This is when the engine is partially torn down, the rings removed, the cylinder bored out, new rings put in, and the whole lot put back together again. I'd look for a cheap mechanic since the car is 20 years old. Ya might think about trading it in or selling it outright.