Why do headlights turn yellow?
It’s not dirt, and it’s not age exactly — it’s a coating failure you can actually reverse. Here’s what’s happening on the surface of your lenses.
Plastic, not glass
Since the 1980s, most headlights are made of plastic — lighter, tougher, and cheaper to shape than glass. But bare plastic is not happy for long in the sun.
What speeds it up
- Sun exposure — cars parked outside, especially facing south or west, yellow faster.
- Heat — the area right by the bulb runs hot and ages first.
- Harsh chemicals — some cleaners strip what’s left of the coating.
How to slow it down
Park in the shade or a garage when you can, avoid abrasive cleaners, and keep an eye out for oxidation. Oxidation will usually begin on the corners of the light but once the oxidation spreads to the front of the lights have it restored. Do not wait until your lights turn yellow or cloudy! It is much better for your lights to be restored early before yellowing begins.