Gas and Oil Home Heating Furnaces - Rheem oil furnace smoking

Hi, anybody have any thoughts on this? Last March I noticed there was black smoke coming from the chimney. I have a Rheem oil furnace which is about 10-12 years old. A technician came out, cleaned the furnace (wasn't done for a couple years) and replaced the nozzle. The next day I noticed that it was smoking again, I called and they sent him back out. He said he made some adjustments and replaced the nozzle again. Seemed to work OK for about 2 weeks and then it started again. He came back out and did the same again. He said that a little black smoke was going to be normal because the combustion chamber was burning old fuel. I did have him check the heat exchanger to make sure that it wasn't cracked or leaking and he said it was fine. This fall when starting the furnace there was still a trace of black smoke from the chimney but not anymore than last year. Tonight I noticed coming home ALOT of smoke coming from the chimney, so much you could see it in the dark blowing across the road. I have a carbon monoxide dectector I bought last year when this happened, and it says that it is not picking up anything. I am going to have to call somewhere tomorrow, (obviously not the same place as last year, even though everyone recommends them) but anybody have any ideas what this might be? Or anything I should be asking or looking for?

did this guy do a smoke, draft, stack temp test, or was going by eye??

If he was doing it by eye, yes dump him!

Call your oil dealer and see if they have a tech on the team, or who they would suggest for a good oil tech.

Oil should NEVER have smoke when it's all tuned in right.

He had some equipment that he stuck into the pipe going from the furnace to the chimney. He did make a comment about temperature falling in the normal range, so I am going to assume that he did check this with his equipment, but I guess I can't say that for sure. He also adjusted the little flapper door on the pipe from the furnace to chimney because he said it wasn't opening enough.

It's time to find a new tech & fast. As Jay said, you should never see smoke from your chimney.