It's getting towards winter and more darkness, so more headlight running.

I have had several cars with the plastic headlights, some 740's and 2 940's. I now have a 940 with the glass lens and the foglight next to the grille.
I have cleaned the others, the plastic ones, both using scratch remover on the lens and removing the whole assembly from the car and cleaning the internal reflector and inside of the lens as explained in the FAQ. This worked great.

The new car with the glass lenses looked good, but I was unhappy with the light output. I posted about this a couple of months ago, and took some voltage measurements; it appears they get system voltage around 12, but not batt voltage of 13. something. But they were not down around 8 volts so I did not think this was the sole source of the issue. So I removed them from the car and cleaned them internally, using warm water, alcohol, and a little dish soap and some agitation of the solution and then several rinses and letting them dry, again as explained in the FAQ.
What a difference. Doing them one at a time shows how much the reflector shines up; it is amazing and I now have actual headlights. They could be better still and I may put in some relays so they get batt. voltage, but there is a clear difference.
Just a tip, it worked for me.