3M makes a decal adhesive remover in a rectangular can with a small spout. O'reillys and other auto parts store carries it. I have used it literally hundreds of times and has never harmed the surface. Be very careful of the Rustoleum spray can of decal remover....it is not kind to every surface!WD-40 is a safe adhesive remover. Try spraying it down and let it soak a few minutes. My last use was to remove two sided carpet tape from wood floors.