Many instrument panel and most head light lenses are made of a plastic
called polycarbonate.  It is used because the strength of the material
(same material used in bullet proof "glasses").

The only problem is that polycarbonate does not have the chemical
resistance or sun light (UV) resistance that some other plastic
materials do, thus yellowing and fogging occurs easily... but hey, they
get to sell you the spares...

Good luck!

hello,
the plastic screen that covers the
gauges on my 01 frontier is covered
with a film of some sort.
i wipe it with windex but when it dries the
fog returns.
any thoughts would be greatly appreciated.
                    dick