Headlights with an aged, cloudy, or hazy look are becoming increasingly common, as the average age of all cars on the road continues to rise. Plus, most modern vehicles use replaceable bulbs with plastic lenses that are more prone to discoloration, rather than the more-durable glass sealed-beam units. Fortunately, our tests show that for a modest cost, even junkyard-ready lens covers can be made clear again.
More than a cosmetic issue, clouded lenses can pose a serious threat to safety, compromising night vision and reducing the effectiveness of your headlights by up to 80 percent, based on our measurements.
Ultraviolet radiation from the sun is the primary culprit in the headlight aging process, compounded by other environmental factors. The problem tends to be most serious in warmer, sunny climates, but we've seen plenty of evidence of it in northern regions, including on employee cars in our own Yonkers, N.Y., parking lot.
Some makes and models seem to be more susceptible than others, depending on the size, angle, and composition of the lens, and whether the car is garaged or spends its life on the street. The effects can vary from just a slight haze to making lenses virtually opaque.
Some manufacturers have responded to this trend by offering products to restore damaged lenses. The products vary in price, ease of use, and effectiveness, with some requiring power tools while others need less than an hour of your time. Most require several steps, but the results can be well worth the effort. Our testing has found that they can make a big difference--particularly if you don't rush the job. And they can restore old headlamps for far less money than it would take to replace them.
We recently tried four products on dozens of headlights, and our tests show that even the poorest performer of the bunch can dramatically improve light output, depending on how badly the lenses are weathered. All cost less than $25.
How we tested
Using cars with clouded headlights belonging to CR staff volunteers, we evaluated products for their effectiveness and ease of use. We measured the change in light transmission before and after working on them in one of our labs, with a light meter and with controlled light sources. Mounted on a stand, the light meter was positioned in the brightest part of the light beam, and left in the same position for the "after -restoration" measurement. After returning the cars to their owners, we brought them back into the lab eight weeks later to re-check the light transmission and see how the products held up over time.
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