If You Want An Honest Mechanic You Can Trust With Your Life, Paul Cowden Is Like No Other. —
I've been going to Paul for more than 25 years, three cars, almost 500,000 miles and six changes of residence. I wouldn't trade him for anyone. He not only tells you what is wrong with your car, he will show you as well (he keeps a well stock parts demo bin under his desk).
He's also great about working within your budget and tells you honestly what needs to be done now and what can wait.
His shop is open from 7:30 am to 6 pm four days a week. Perfect hours. He is a brisk 15-20 minute walk from downtown San Francisco so getting to work is easy.
He always keeps you informed on what he finds and lets you know what to expect. He is not the cheapest mechanic in San Francisco, but he is certainly the best. He works mostly on Japanese and some European makes (I have a Volvo) so call ahead.