I haven't used it in my GMC but I have used it successfully a number of times. It's great stuff. I had a mower that wouldn't run I put some sea foam in the gas and sprayed some carburetor cleaner in the carb. and it started and has run great since. I had a 150cc motor scooter that had a gummed-up carb from using 10% ethanol gas and had severe running problems, and wouldn't go over 20 mph. I put some Sea Foam in the gas and went for a short ride and by the end of the ride I was easily doing 55 mph, and it's been fine since.