Joe,
Though commonly used, VCT tile is not recommended for garage floor useage. It stains very easily from petroleum based products and subfloor (concrete) staining due to moisture. If insisted upon, a calcium cloride (moisture pressure) test should be performed on the concrete and an epoxy adhesive used. After install, cars should be parked on a (non petroleum based) pad as the tires will leave a stain. VCT uses vinyl in their make up and that is where the problem lies at it is very easily stained. Fritztile makes a tile that is made up of stone, slate, marble, etc chips held together with a resin and is less susceptible to staining (or at least being able to see the stain).
Rick