Car Zone in Union Square is, without a doubt, the best garage/mechanic I've ever used in my life. Murph and his team are honest, fairly-priced, and incredibly helpful in keeping an older car alive. We have a 1993 Corolla that we use as our in-town car that, while not pretty, is still running almost 300k miles in thanks to him and his team.

While not right in Davis, it's a short walk to Bloc 11, Neighborhood Bakery, or other places to hang out while they do the work.

https://goo.gl/maps/cmN1x9uCezL2