Re: black streaks
We sell a product (and use it all the time) called Reliable. It will clean anything you put it on. Your camper, awning, grill, boat, car, truck. And with has no harsh chemicals that will ruin decals or paint and will not scratch. If you want more information, private message me and I will be happy to get you some.
Several people here have gotten it from me and all will say it works.