Well - thank you Joe. I stand corrected and will be eating crow with my friends!
AND - trwmodela - thank you for prompting me to hit the scales. Time for a diet for me and the motorhome! We were 500# over GVWR!
Since we are now home - we will be unloading the MH. I will leave the bike rack and TOW hitch on and hit the scales again. I have no idea how we we will get rid of 500# though. Will have to start with not carrying ANY fresh water (makes it hard to flush the potty on the roll.)
But - back to the MPG discussion at hand. No doubt 500# extra is making a small difference but we have done some trips WITHOUT the TOAD and have not really seen much improvement (maybe 0.3-0.5 MPG better at best.)
Averaged 7.8 mpg from Southern Indiana through KY, WV, VA and back to Chapel Hill so pretty consistent pulling the TOAD through the Appalachians.
Bottom line - my experience is you won't consistently see north of 8.5 MPG in a 3170DS running 14.5K (or 15K if you are dumb like me). Hang a TOAD and you won't average over 8.
BTW - I ran all the way through WV,VA, and NC coming east without cruise control. Tried my darndest to keep it out of the 3K+ RPM range and eased up the hills as slow as 45mph on the way home. Got 7.8MPG vs the 7.9mpg on the way west using crusie and letting it settle in at 3-3.5K RPM on the big grades. So I'm not convinced that RPM/Gear makes a huge difference for the same grades and speeds. I do avoid 4K+ RPM as much as possible cuz it scares me to have that much mass rotating that fast just under my feet. I don't think that these engines are blueprinted and balanced and it is plain LOUD!