Go to your local GMC dealership and ask for the stuff they use on trade ins to get them clean. My hubby used to work as a mechanic at GM and used the stuff all the time, works like magic. I can't remember exactly what its name was though. It may cost a little more but your paint job is worth it. Too many over the counter products destroy the paint job. Another little trick, since you probably have light upholstery with a silver truck, white gas works awesome to get out any and all stains. Again you can ask at the dealership, they should have it on hand.