I remove to 3 stickers behind the gas cap using the recommendation of WD 40 it took me 30 seconds and you can not tell there were ever any stickers there.
I usually use the hair drier or heat gun for the removal of stickers. Then i apply the thinner or alcohol for the removal of residue. But it is necessary to use the nails for the removal of stickers when we use hair drier. Peal them off from one corner and gradually do it.