Removing those ugly gas stains from under the fuel filler of your car or truck can be done with a little elbow grease and common cleaners. The stains come from gasoline damaging the clear coat or wax on the finish. If you keep your car waxed it will be easier to remove these types of stains, but even if you have never waxed it, they can be removed.
Wash the car or truck with mild soap and water. A good automotive wash will give you the best results. Use a soft sponge or microfiber cloth and a mild soap so that you do not scratch the paint.
Apply a coat of high-quality automotive wax to the area. Rub the wax off with a soft cloth or rag according to the manufacturer's directions.
Buff the area with an orbital buffer to restore the shine to the finish. Use a low-speed buffer so you don't burn though the clear coat during the buffing process.
Wax the area again and rub it off. Buff the section of paint again. Continue buffing and waxing until you have completely removed the gas stain from the paint.
Apply a coat of wax to the entire vehicle to even out the finish and protect the paint from further stains and the elements.
Wax your car at least twice a year to protect the finish and keep the paint looking new.