Washing my '09 189FDS
My all the product literature, LOL, that came with my unit was a small brochure about the roof sheeting. The brochure recommended Murphys Oil Soap for the roof. I just put about 2 oz MOS in a three gallon bucket of water and use it on the roof and body. MOS is a vegetable oil-based soap, so it's milder than synthetics or mineral-based. you get it at Lowe's by the quart or gallon.
2009 FF X-189 FDS
2011 Chevrolet Z-71 LTZ 4X4 p/u.
Reese WD hitch
Patient and understanding wife