I may get wrist-slapped for this but I have found that rubber roof cleaner works fantastically on awnings. It also cleans plastic parts (like MaxxAir domes, A/C shroud, LP bottle cover, etc.). I prefer "Best" brand...expensive, but effective. If there is some dark staining, I use a citrus degreaser product I buy from the local RV parts dealer.
TT: 2010 Flagstaff 27BHSS; TV: 2002 F-250 Lariat Crewcab 4X4, 7.3L Powerstroke, 3.73 LS
2015: 11 total days camped
Huntsville Space Center, AL; William Bankhead National Forest, AL; and Gulf State Park, AL