After applying a couple of coats of wintergreen oil - alcohol to the new to me- defroster vents (far left), the gray white on the exposed surface was still present. Decided to see if the trim cleaner I got years ago would improve it.
Decide for yourselves but I think its much better. Second from left in photo below. Put both the wintergreen oil and the trim cleaner on the originals as well.
(The reddish brown is what the painter sprayed the black ones. He didn't charge me, so I can't complain. LOL. He's a nice guy.)
Here's the Trim stuff. Haven't been able to find very much about it.
No smell of wintergreen in it.