Re: 300M Headlight lens restoration - posted in Allpar. The best way to prevent this situation, if possible, is to apply 3M Rock Guard material to the lenses. I had a 2000 300M since new and after 11 years, the lenses were becoming pitted from salt and sand on winter roads. Had the material replaced and when the old material was removed, the lenses looked like brand new. A possible fix to the problem of lens deterioration after the lenses have been restored, is to apply Rock Guard after the project is completed.
(Suggestion: Have had all my new vehicles front ends completely covered with Rock Guard (since 2000) and although a bit expensive, is less than the cost of a new paint job and if it becomes necessary to replace it, keeps the paint underneath free from rock dents and chips and the paint still looks like new. This material is tough stuff and has kept my headlight, signal light and fog light lenses from breakage.)