2002 gmc envoy_slt
If you're talking about the black plastic and not rubber, for example the step plate on the bumper or rear glass handle, most of the 'treatments' only cover them up temporarily. (I've tried several and unless you really work them in, the effect washes right off). What seems to have some lasting effect is to get a good nylon/polyester covered sponge or fairly stiff bristled brush and scrub the heck out of them.....the lightening on those textured plastic parts is more deposits than fading. Once or twice a year I simply scrub the heck out of them using a good auto wash & water mix, which removes all the film making them appear faded. - I was shocked to say the least that its deposits and not fading. It takes some elbow grease, but those black plastic parts will again appear black or at least charcoal in color. You can then follow up with a light coat of your favorite detailing plastic protectant.