You shoot yourself in the foot if you insist on supplying your own parts. First, you limit yourself to the lower tier mechanics who will take on any kind of job because they need the work. Second, you have no recourse on the outcome of the job, if/when it fails. If it doesn't fit, you are out the cost, so far, for the mechanic's labor, unless you chisel him out of his labor and his materials margin.
Just bad policy.
Different areas, different norms. It might be so in Southern California but I can assure you that it's not that way in Mississippi. The guy I normally use typically takes 1-2 weeks to get a car into his shop, he's that in demand. He's far from second tier. If there's any fault I can find with him it's that he's so busy it takes forever to get your vehicle in. The reason he's so busy is that he does good work at a fair price and he'll do what you want him to without trying to sell you stuff you don't need. The diesel shop that I've used that tries to push bully dog parts can usually take you right away, he's usually sitting there watching TV when you drive up.
Quite frankly I don't worry about having recourse, I trust the guy. In 15 years he's never done me wrong and vice versa. I know that if something breaks and it's his fault he'll fix it, if it's a bad part I brought him then I certainly don't expect him to. Most of the time I use the parts he gets himself since he owns the NAPA parts house next to his shop. If I want something special like my uprated clutch he'll just say bring it in though, no questions. In a few months my 2006 jeep liberty diesel will need a timing belt replaced, since they only made 5000 of them the parts for the VM Motori engine aren't going to be something he can get through his supply chain, I'm going to get them myself and bring them in. We've already talked about it.
I suspect it's just the difference in the way things are done between So Cal and small town Mississippi more than anything else.
