I have a really hard time deciding whether to tip or not. Mostly because I'm one of the people who are pretty illiterate when it comes to things automotive. I mean, I can change my oil or change a flat tire, but besides that I have to take the word of the mechanic. The only things I can do are look online for pricing and problem diagnosis, or get advice from other people who are better with autos.

I just had $400 worth of work done on my 1997 Blazer for a new starter and differential cover, and checking the error codes from the check engine light. I knew I needed a new starter and diff cover, but I don't know how fair a price that is. So how do I know if I should tip? It could have been a great deal, or they could have totally ripped me off. If I knew I was getting a good deal I'd most definitely tip, but how dumb do I look when I give them a fat tip after they just took me to the cleaners?