Hi Denis
Firstly you can remove the black streaks with a small amount of white spirit on a piece of cloth. Becareful of black streak removers as they can be quite aggressive and leave a dull surface if used regularly. As you have a new van and so hopefully as yet no black streaks you should use a shampoo with polymer (Kemdirect Shampoo) which put a protective coat on the surface and prevents black streaks from coming back as they as easily washed off. You can also make the rubber water repellent by using a silicon spray on a piece of cloth and grease the rubber and this also preserves it.
When using Kemdirect Shampoo it gives protection and gloss all in the one wash and is safe to use on your car as well. Your van will look as if you have waxed and polished it, when you do not need to with this product. Have a look at kemdirect.com where it will tell you about this new range of products.
Hope this help you..happy caravanning Joyce
