We have a 2002 Winnie 32V. We've only owned it for ten months but during a five week trip thru Vegas, over to Page/Monument Valley and up to Canyonlands, then over to Cedar Brakes and up to Great Basin then over I-80 and across to Ft Bragg, up the Coast to Cape Disappointment/Ft. Stevens, down to Winchester Bay, OR and then over to I-5 and south to Home all the time pulling the GV(3200#). I don't have the log book with me but that's a fair piece and we got an average for the entire trip of 7.5MPG.
I try to keep it 58 to 60 MPH, use the CC a lot even in the hills.
I do get 1.0 MPG better(+/-) without the towed and with the 1995 Sidekick(2700#), about -0.5 MPG. We have about 34K miles but over 500 hrs on the genny so we feel it was a sit and park RV for most of it's life. We do have the full Banks Power setup, intake, 3" exhaust w/headers, Banks transmission control and program. It is fully CARB compliant and passed the required Smog Certification in Feb of last year.
Got six last week when we got caught in two hours of stop and go traffic on some of the freeways in LA County on our way home.
I never looked at it from tommy-g's point of view, I will factor that in on the next trip. Then I can say I get 13 MPG city and 17 MPG highway. :B