I am a mechanic myself and very rarely get tipped. I work on boats and the customer is almost never there so there is no one to tip me. But on the occasion that it happens it is a really nice gesture. I never go into a job expecting it though and would not do my job any differently whether I was or wasn't tipped. I just see them as an occasional pleasant surprise. Tipping is up to you if you feel he did a good enough job to have earned it then yes pay him. I just hate how tipping has become soo manditory these days. Kinda defeats the purpose IMO.