[DrRadar]

I once tried a TurtleWax kit which was ineffective. Earlier this year, I used Meguiars's Clear Plastic Cleaner (#17) and Clear Plastic Polish (#10) and wet sandpaper. Following the instructions provided at http://www.techguys.ca/howto/polish_lenses.html significantly improved the condition of the lenses. They were not like new, but they were much better. I spent $30 on all the materials (both 10oz bottles cleaner/polisher and wet sandpaper [from the parts store] with a variety of grit between 600 and 2000). I've done two vehicles and have enough stuff for many more.