I am a mech. by trade. I work on all kinds of vehicles in our fleet from the 2008 Suburbans that are lifted, up-armored HMMWV's, loaders, back hoes, minivans, and Riverine boats.
The only time I wear Mechanix is when I am working with something where I know I would cut my paws (broken windshields, rust, knuckle busting areas) but I don't always wear them when doing that stuff. I would say 30% of the time I wear them when those risks are present.