Like checksix, I'm a mechanical engineer by trade... My advice, however, is to avoid getting too deeply technical with your mechanic. A discussion involving coefficients of friction varying with temperature, or "stick-slip" phenomena, may earn you a "that's a lot of hooey" response, because everyone knows we engineer types never leave our desks and deal with real-world hardware and problems. (Sarcasm now switched OFF.)

Not demeaning mechanics by any stretch, but in my experience it is a rare one indeed who will listen to a technical explanation from someone who doesn't repair cars for a living.
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In God We Trust. Everyone else, keep your hands where I can see them.