Have you ever noticed how your car's headlight lenses often turn cloudy or yellow over time? Many companies sell kits to buff the shine back into them, but cosmetics aren't the only reason you should keep a close eye on the condition of your headlights. Indeed, that's not even the best reason: According to the AAA, cloudy or yellowed headlights may "generate only 20 percent of the amount of light that new headlights do." That's right, your car's candlepower could be down by some 80 percent just because the lenses look hazy or yellowed.
In findings detailed in a release Dec. 11, the AAA tested the weatherbeaten headlights of 11-year-old sedans and compared their output to those of new replacement headlights. On the vehicles' low-beam settings, the cloudy headlights provided just 22 percent of the illumination of a new unit. (AAA testing has shown that even new, state-of-the-art headlights provide only 40 percent of the sight distance of full daylight, and that's a best-case scenario).
But the motor club's research also revealed that replacement headlights purchased through the aftermarket failed to provide the same performance as new factory parts. They returned between 83 and 90 percent of a new OEM replacement part, and as Triple A notes, "these did fail to meet certain requirements for light intensity and were found to be more likely to produce glare for oncoming traffic."
Interestingly, the AAA also tried some headlight restoration options -- both professional and do-it-yourself kits -- and found that they returned the lights to only around 70 percent of their as-new performance, and they produced "more glare than is acceptable" based on Department of Transportation criteria.
Even so, given the often prohibitively expensive cost of new replacement headlight buckets, a home restoration kit is better than nothing. Roadshow Editor-at-Large Brian Cooley recently. You can read about which one he liked best .
So, what causes headlights to degrade? Ironically, perhaps, the answer is primarily sunlight. Just like with your skin, long-term sun exposure can damage the surface of your headlights, eroding their plastic coatings and causing the haze and yellow finish that absorb light output before it can illuminate the road ahead. The AAA's findings don't mention it, but dust, rocks and road debris can further pit and damage headlights, accelerating the deterioration of their performance.
The takeaway from all of this? Inspect your headlights regularly, especially with a vehicle that's three years old or more. If you encounter such damage, bear in mind that a few hours with a DIY kit or a restoration job at a professional automotive detailer can help greatly, but the best solution is to dig deeper into your pockets and replace your headlights with new units manufactured by your automaker.