In my experience (strictly with 240s now) the yellowing is on the outer surface. Over the past 25 years owning 240's I've polished the lenses a few times, stopping short of finding a UV coating to keep them clear. Spent hours with 3M paint compounding polishes, plastic restorers, and elbow grease. They look nice for a season, then they're dull again.





Then, I had a wiring harness problem under the left strut tower caused by a rodent. To effect a repair to be proud of, I needed to pull the harness all the way back from the horn, and to do that, remove the left headlight assembly. Oops, the plastic adjuster assembly crumbled when removing the lamp. I checked into getting a new one finding it only $100 for an aftermarket lamp assembly. The entire thing, lens and all. I got a pair of them. Dec. 2021.

Now, this photo I took today, Sept. 2024, almost 3 year later. It still looks brand new, clear as crystal. And no, the car is not garaged.



Makes the car look so much better. Best $200 I ever spent on transportation.


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Art Benstein near Baltimore

"Middle age is when a narrow waist and a broad mind begin to change places." -E. Joseph Cossman

Lots of products out there, so in addition to checking out their ads, look for independent product reviews and comparisons as well as checking out the DIY Youtube videos.

I ended up going for the highly regarded and more expensive Osram/Sylvania headlight cleaning kit and would use it again. Biggest downside is it's a multi-step hand rub kit, so a lot more work than many of the other kits. Count on a couple of hours per bulb to do a decent job as well as a pound or two of elbow grease. Not perfect and a lot more manual effort than the others, but done properly the results are decent and I think worth the extra time and cost, plus with their sealer you get a lifetime guarantee that none of the others offer. Cheapest I could find was on Amazon.

Please realize, you're only doing the exterior oxidized and UV damaged plastic. Depending on how bad yours are, up to half the problem can be the back side of the lens and the plastic reflector. The kits will make a significant improvement, but if the results are still unsatisfactory you may wish you'd bit the bullet and just gone for new headlights. That's kind of where I was ending up, but now that I've switched to LEDs I don't need the insides to be any better, in fact if they were any better it would make the LEDs even more bright than they need to be. Getting an Osram kit to do my other 940 is still on my shopping list.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now