From CMA:
Warning: Xenit is a stain extractor. Do not use on plastic and always test painted surfaces in a less noticeable area prior to using. To remove tar, bug residues and tree sap from automative finishes, use Stoner Tarminator
They have 3 "Xenits" in the search, all with different tiles, same bottle, aerosol type. Same price. One says don't use on plastics, one makes no mention of plastics and the other says don't use on CLEAR plastic.
With that much confusion from the retailer, I'd rather go with something someone KNOWS works *ON* plastic.