Tried peppermint oil, dryer sheets. Does nada. Best defense against mice is a cat colony. Nothing like a feline walking from under your rig with a big, fat rat in its mouth.
Next to cats, snap traps work, but make sure they are the wide-trigger type (JAWZ brand, for example), so they are usable with/without bait. Sticky pads work as well, but make sure to note where they are, and keep them out of the way of other animals.
I have seen a poison (called RatX) offered at Lowe's which uses corn glutin meal and salt. It must be kept dry, but apparently it is usable against mice/rats, since they will eat it, not bother drinking water then expire. Because it is "just" salty, it isn't really toxic to other animals.