The back window of my car is flexible vinyl, the guage plastic is hard plastic - don't know exactly which one. I suspect it is the same plastic as the signal light lenses. So far, the gauge plastic of xtoy or miatank is unscratched. Wipe the dirt off with non-abrasive materials, don't rub it in. Others have had success with 10/17 on the guage plastic if it is already scratched. I use it on the car's rear window and to detail plastic signal lenses. I have no reason to doubt that it will work well on the guages as others have reported.

dave and xtoy - don't scratch it in the first place