For those of us with the "yellow-ing" of our headlights.
Try the following, it worked for me;
1) Remove headlight covers from car.
2) Use a metall polish (for aluminum or stainless steel) and polish light cover following directions on polish.
3) May need to repeat step two a couple of times.
4) Using a car polish (for cars with clear coats), polish headlight covers following directions on polish.
5) May need to repeat step four two or three times.
6) Using car wax, wax the headlight covers.
7) May need to repeat step six two or three times.
Can't tell the difference between a new headlight cover and the now revitalized one.
