Like many people, my front headlights are suffering from fogging and discolouration... As one side was ok and the other really, really bad. I thought I'd try the toothpaste method and see if that had any effect. Below are before and after pics... This was after just a few minutes of cleaning, then washing of with warm water and a damp cloth. Then drying with a fresh cloth. As you can see, it's clean up a huge amount, smoothed out some of the scratches, got rid of the discolouration... but hasn't removed the fogging to the actual cover itself. I suspect that a lot of this is on the inside and if they can be opened up without too much trouble, it might be possible to clean them up from the inside. Of course if replacement covers can be bought... it would probably be simpler to do that unless they're ridiculously expensive. I think this is one of the Japanese quirks as it's never happened on US or EU built cars with plastic headlight covers that I've owned... Maybe I've just been lucky in that regard. If anyone has any better suggestions and pictures of results... please add them. Oh and in case any one was wondering... I used Colgate whitening toothpaste... and yes... my headlight is minty fresh.