2008 Audi A4

I'm selling an audi a4 sline 20 tdi from 2008, the car looks good, the only problem is that after 2800 revolutions, it revs on the spot if you don't exceed 2800, there is no problem, I went to the mechanic and he said that the problem is from the oil in the box, filters and oil need to be replaced the costs would be about 240, I don't want to do it again because I have another lot