Like on my boat for instance I had an issue with it only firing on 2 of 4 cylinders. Well I took it to a guy who charged me $400 and it worked good for one boat trip, then a month or so later I took the boat out again and it went back to doing the same thing. Imo if I were a mechanic and I couldn't fix it I'd at least give a portion of the money back that I charged. The part that irritated me was that he didn't seem interested in taking another look at it after that. Good way to retain customers, just tell them f off after they take your money.