[genocidicbunny]

I've never tipped a car mechanic. They bill their labor rates anyways, tipping in such circumstance should never be expected.

Generally, most tipping is at restaurants and bars/pubs. Hairdresses/barbers/salons is also very common because of the close personal interaction with the worker.

Most of the time you tip at businesses that would be expected to employ low-education, or poorer or immigrant workers (and by extension, more easily abused workers.) Restaurants, salons, car washes, etc, all tend to employ poorer, less educated people, and also tend to be highly tip-based businesses. So for the most part you're expected to tip at businesses that traditionally abuse and underpay their employees.