We've actually heard of using lighter fluid to remove sticky residue, so there's probably some truth to what your friend is advising. However, personally, we'd recommend a tar remover like Autoglym Intensive Tar Remover - which you can buy for about £6 or you can buy the kit (remover plus microfibre cloth and applicator pad) for less than a tenner: amzn.to/31G1J1I