I`ve always used charcoal starter fluid to remove road tar. Works like magic! I`ve never tried it on the tail lenses though. I`d be afraid to put anything harsh on light lenses. There used to be a car wash detergent that was made for cars that had tree sap,etc. that the more gentler soaps wouldn`t remove. I used it years ago on an older car that I didn`t have room for in my garage. I can`t remember the name of it,but I got it at Autozone.
