Wow, that sounds bad.

Try polishing compound, then wax or polish. It might take a few rounds with the polishing compound before you can see the end result. Go in a circular motion and you'll immediately feel the debris grinding off of the lens. The polish/wax finishes off the job nicely and prevents them from chalking again. And they look better on the front of the car.

IF the lenses are so weathered that they have big canyons in the finish, it's new lens time. No amount of polishing can restore the worst lenses. Still, I have luck de-weathering some of the worst Ford lenses with it. With very good success, I might add.

You can also use plastic polish but it can be hard to find, and is usually expensive. I usually have some on hand for marine use. It's primarily meant for plexiglass windows and places where you can see fine scratches. Fog lights aren't a place where you'll notice any tiny marks.

Apparently some people have used metal polish on this as well, but I always used water-based polishing compound.
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1992 940 wagon, 72k
make people envious; smile often.