This is a very polite way of asking a question. Use it when the listener might not have an answer for you, or might not want to give an answer.
In the example above, you're asking the mechanic for the name of another mechanic who works on the kind of car you have. He might not know of a good answer, and even if he does know he might not want to tell you because the other mechanic is his competitor in a way. So it's good to ask in a polite way.