I know that it sounds suspect, but if that doesn't work, go to Advance Auto Parts (probably *any* auto parts store, but Advance is everywhere, and I know that they have it) and look (or ask for) "3M Adhesive Remover" (I believe that the actual name has 2 other products in it, like "Adhesive, Wax and Tar" remover. It's in an 8 oz bronze and black tin in the auto-body section.
I've used it on sticker goo on a number of articles of sticker-covered-and-run-through-the-wash clothing for my boys, on both natural and synthetic, colored and white clothes. (Last time was a white and dark blue soccer jersey (like a rayon) that had a lot of sentimental value, as we'd gotten it in Rome.
The white was unstained, the blue was unbleached and the synthetic material was unmarred after a thorough soaking as I removed the stuff with a washcloth. I don't know about tar or wax, but the stuff just dissolves sticker adhesive away without harming the material. We now have a tin that lives in the laundry room full-time.
-Scott (S.'s Hubby)