Assuming that you have thoroughly cleaned them with the proper juice - try a variety of them, including white wall tire cleaner and a brush, and they are still discolored, you can buy a spray vinyl finish at many auto paint stores that will give you a new vinyl look. Be sure to do a clear top coat over the color coat as it greatly improves the wear.

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'76 240D-Sold
'78 240D-Sold
'85 300 SD, 165K-Sold
'88 300 TE, 165K-Sold
'64 Porsche 356C Cabriolet- under restoration
'86 560SL 124K Miles-Sold
'94 320E Wagon, 74K Miles-128K Miles JUNKED
'06 E350 Wagon, 84K Miles
07 SL550, 14K Miles