Hi I use Korkay Awning Cleaner & Black Streak Remover # 196 works well this the product discription
Formulated for the RV industry to take off those ugly black streaks and dirt on the sides of your RV. Also removes bugs, tree sap, pitch, air pollutants, and other grime that collects on your RVs exterior and awning. Once you try it, you’ll be amazed!! Safe for RV’s decals, gel-coat, fiberglass and painted surfaces. Works great on vinyl siding, boat hulls & covers too!!!!!!
Available in; 32oz, 1, 5, 15, & 55 gallon sizes. ( cheaper by the gal. i paid about $8.50 for 32 oz at a local camping supply store) link
http://korkay.com/p_1.htm good luck