My previous motorhome was a 32' 1999 with the 4 spd.
My new motorhome is a 35' 2012 with the 5 spd.
Although it worked hard, I pulled my 20' enclosed trailer behind my '99 to Windrock and my flatbed to Moab and SD. I sold the enclosed because I didn't feel the motorhome was up to the task of going through Colorado. Overall average with that rig was 7- ish mpg. The package with the enclosed weighed out just about at 26,000#.
I have not weighed the new setup.