I have a class A with a fiberglass roof. I park it along a tree line in the summer & inside in the winter The roof is black on about 25% of it. I got up there today with a bucket of oxyclean mixed ...
Awesome cleaner from the dollar store does a great job. We park under trees all summer also and have to clean it 2X per year. Mean Grean also has a specific mildew cleaner that can be found in some dollar stores. That works too.