The polycarbonate plastic headlight lens on your car or truck begins to degrade from the moment it leaves the factory. Air pollution, airborne grit as the vehicle is driven, and the effects of various wavelengths of ultraviolet light act together to mechanically and chemically degrade the lens, making it hazy or yellowed. This explains why so many companies have gotten into the car care market with lens-renewal products–boxed kits consisting of abrasives that grind off the yellowed layer and smooth out scratches. Some even contain a UV-resistant coating that you wipe or spray on. You can find these restorers everywhere from your local supermarket to hardware stores to car parts stores. We were pleasantly surprised by what we found in this test, but having said that, there are still a few things you need to know.
How We Tested
We tested these products on cars that exhibited moderate lens degradation, but we also paid a visit to our favorite auto salvage-recycling yard, Scarpati’s in Trenton, NJ, and asked to pick out three badly-degraded lights. They thought we were crazy, until we explained what we were working on. Here’s what our tests revealed. Lens restoration products will quickly restore a dulled, yellowed, and scratched lens. They can’t address dust, the effects of sunlight degradation on the inside surface of the lens, or the accumulation of condensation and dust on the reflector. Furthermore, most of these improvements are not permanent. And the degree to which they last depends on the region where the car is located, the amount of sunlight it sees, and a range of factors, such as air pollution and dusty driving conditions. Meguiar’s lens restoration kit even tells you on the package that the improvement is rated for one year. It may make more sense if the lens is badly degraded to buy a replacement headlight assembly from a local auto parts store or online from an outfit like Headlightsdepot.com.
All of the headlight lenses were first cleaned with either water or ordinary household cleaner to remove surface dirt, a step that all the kit manufacturers recommend. Then we applied the products per the instructions. We didn’t improvise. We read the directions and followed them.