I wouldn't use anything on them, maybe wax if you wax your car. We just bought a 2019 ES, and traded a 2010 ES. The lights on the 2010 looked like new when we traded it in. The Lexus lights just seem to be made from a better plastic. We also have a 2018 XSE V6 and a 2011 Camry V6 SE. The 2011's lights are in pretty good shape, but not as good a condition as the 2010 ES lights. We have a lot of cars besides those, also. Had a Subie and the lights went to crap fast. My Mustang, the same thing. The lights on your GS should be fine for a long time with nothing on them.