Beating a Dead horse...Roof Cleaner\Conditioner

I too have a TT with a roof that doesn't need anything. Its supposedly impregnated with UV Protectant. Per owners manual, I wash it using a mild dish soap 3 times a year. Clean roof and a nice coat of wax on the sidewalls, black streaks are almost non-existent. If I do get them, they come right off with normal washing