Cleaner For Plastic Grill?

[JasonATL]

The grill on my 1999 RX300 has dark spots on it. The grill is plastic (I assume). What should be used to clean it? What about protecting it for the future (and protecting my new RX 400h grill)?

I'm going to clean the lenses with Meguiars PlastX, but it appears to be for "clear plastics". So, should I avoid PlastX on the grill? What about 303 Aerospace Protectant to use as a protectant?

Any advice is appreciated.