We just bought a car from a private seller. They got the oil changed before the put it up for sale (very nice of them), and they warned us that when they got the oil changed the car's accordion tube coming out of the air filter was covered in duct tape, when confronted the service people said they had no idea.
Then I took it in for my mechanic to look over and the oil cap was busted and they showed it to me to ask if I wanted them to cut it off, because that was the only way to get it off!
I asked the sellers where they had taken it and if they knew about the damage, they said Big O in Centennial Hills, and they had no idea.
I know the sellers, so I believe them and am not impressed by shady mechanics :(