Is it plastic or fiberglass? IF its fiberglass, and aging, that's pretty much what it does as it ages. You can try refinishing it with Rustoleum Topdeck walk on grade marine paint.
If its Plastic, you can try what's called "Retrobrighting", which requires Hydrogen peroxide paste, saran wrap, UV light and some heat.
If done incorrectly, you'll get a nasty pattern on the surfaces.
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'1992 Dodge W-250 "
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