I have the same problem with my 2007 base car.

The black windshield trim is badly oxidized, with a white coat.

Using plastic polish seems to help for a short time, but it quickly fades.

If anyone has found a solution, please post it.

BTW, the insdie of this black plastic trim is white. I know because an errant rock took out my windshield, bounced against the trim and chipped it.

I've tried the back to black vinyl treatment, but it does not go into the surface and help as it does with soft trim. Turtle wax black car polish does not work either. Although it's great on the paint.

I am ready to try black wax shoe polish....