So I got a newer 03 4Runner recently and my old one had some extremely yellowing and fogging lights having been damaged by the sun. My newer one has new looking headlights although you can faintly see that it wants to begin to haze like the other in the upcoming years. Is there something you 4th gen owners use to protect your headlights from yellowing besides washing your vehicle more often and making sure to buff the headlights?

Yes, this is a common problem. I'd recommend sanding your headlights down to remove the yellow haze, then sealing it with a clear coat. If you forget this step, your headlights will yellow again.

Cheaper clear coat means you'll get peeling and yellowing down the road, so I'd recommend a 2k clear (automotive clear coat that's much more durable than a rattle can clear coat you can get from home depot). Looks like you also live in Chicago. Eastwood is about a 40 min drive from the city and they sell a 2k clear that I used with great success Eastwood 2K Aerospray Clear Coat Matte & High-Gloss.

Procedure you'll want to follow:

1. Remove headlights (trust me, will make the job much easier)
2. Sand with 240 grit until lenses are a consistent haziness
3. Sand with 400 grit
4. Sand with 600 grit
5. Sand with 1000 grit
6. Clean with degreaser, then rubbing alcohol
7. At this point, your lens will be cloudy. This is good. The scuffing gives the clearcoat a surface to adhere to, while also being being shallow enough for the clearcoat to fill and smoothen.
8. Spray clearcoat directly onto the lens. Follow the instructions on the rattlecan and wear PPE. You don't want to get this shit in your lungs or eyes.

Don't expect perfection, but the lenses will definitely be clearer. Also much cheaper than new assemblies for +$500 at the dealer

I found the headlight restore kit from Meguires does a nice job of clearing the lens. But the yellow would. Ome back. Then I tried using rainX afterwards and the lens stayed clear for a longer time. The problem with a clear coat is what you have to do the next time you want to buff them again. You can also try a polymer car polish like Nu Finish. Its usually good for a year.

Thanks for the info. It’ll come in handy. However my headlights are not hazed at the moment and I want to preserve the current cleanliness of it. Should I just clear coat it over it’s stock form?

Id still hit it with the whole range of sand paper if your headlights are starting to haze.

If you don't want to put in all the work, you can skip to 1000 grit, clean, then hit it with the clear coat. It's important for the clearcoat to have a rough surface to adhere to. You may still have some haziness under the clearcoat.

Also, if you're using clearcoat, skip the adhesion promoter. I tried this the first time I restored my headlights and ended up with lots of cracking.

if your headlights arent hazed or yellowing now i would not sand them, that will remove all the factory UV coating. sanding is for when they are hazed & yellowed beyond polishing, then as stated needs a new clear coat.

if they are decent now i would suggest just keeping a good wax coat or ceramic coat on them, that will protect them from UV rays & stop or greatly reduce future yellowing. the lenses are small enough that you can hit them with a wax or use the spray on ceramic coatings like from turtle wax etc very quick & easy.

or for some added protection check out turtle wax or other brands of headlight restore kits, they will have a wipe on UV protector, its not a real clear coat, just a strong protector that will also stop or slow the yellowing.

my 08 had some yellowing on the tops from previous owner not doing any maintenance, i used mothers mag polish just by hand & it removed 90% of the yellowing, now all i do is wax them 2-3 times a year or so & they stay clear.

I treated mine repeatedly using a variety of restorative products and techniques. Results lasted 2-3 months at most. I got tired of that routine and just replaced them. You can find good CAPA and NSF certified replacements for about $120 each.

Last year, I got mine cleaned and polished by a shop for $100, but that lasted a little over 6 months. So I thought this was a losing battle, so I went ahead and got brand new headlights, cost around $220 off Amazon, and these came with the halo. I installed them and they look real nice. I'm looking to laminate them with Xpel, which will keep them nice and clean for years to come. It'll be a nice investment where they will always look new.

Bummer. Need to seal them with a UV resistant clearcoat to keep them from yellowing again

That was what the shop did to the ones I replaced, but it only lasted for 6 months. The sun will kill those plastic lenses, but Xpel which was used by a good friend of mine has kept his lenses in perfect shape for past 3 years. It probably wouldn't hurt to put UV resistant clear coat on my new set before getting Xpel on them; double the protection.

What I do is very similar to what Berty K does. I teach auto tech and my students and I do this for teachers, employees etc for $40 a pair. I use 600,800 1200, 1500, 2000 and 2500 grit sandpaper in that order. Go up and down on the first step and side to side on the second. Then switch back and forth every time you change paper. That way each step "erases" the hairline scratches from the previous step. Ending on 2500 will leave you with a very fine haziness. Then we buff them with a 4-5" buffer on a cordless drill using PlastX plastic polish. After a good buffing they will usually look like brand new. Then we apply PlastX plastic protectant. And they actually look even better after that. The trick is to go back and apply the protectant every three months or so and they'll look good for a long time. The only problem is, I haven't been able to find the protectant anywhere except in the Meguiars Headlamp kit. But there are other sealants out there. I'll put a couple of links below including one on ebay for what would probably be a lifetime supply of sandpaper for cheap.
Wet Dry Sandpaper 400 600 800 1000 1200 1500 2000 2500 3000 Grit Assorted Wood | eBay

Amazon.com: Meguiar's G12310 PlastX Clear Plastic Cleaner & Polish, 10 Fluid Ounces: Automotive

Amazon.com: Blue Magic 730-6 Headlight Lens Sealer - 8 oz.: Automotive

Awesome, you're the real pro here! Wow that's a lot of work to be going between these sanding steps. OK, when mine goes bad, I'll drive to SLC to have you work on mine

It actually only takes about 30 to 45 minutes per light depending on condition. It's really rewarding to see the end result when you get one that is really bad to begin with.
BTW: Don't go to SLC. You won't find me there. I'm in Lake City SC.

Thanks for the heads up! Not sure how I saw that as SLC, UT

Is there a reason no one’s mentioned buffing them out and applying Lamin-X headlight film? My friend did that on his LX and they look great even a couple years later.