I'm certainly happy with our almost over-powered 36' Monterey with the 400HP C9 and Allison 6, towing our 4300 lb Explorer. On my last trip from Portland to Hagerman, ID, about 500+ miles of mostly I-84, I did something I don't usually do. I determined to try for maximum fuel efficiency, and I know that the cruise control system has a much steadier foot than I do, so I put it to work. From the start I set the cruise at 57mph, just above truck speed in the right lane, and tried to stay there. Where I had to pass, I took my time and tried to do it without changing the cruise control or stomping on the throttle. Where the speed "limit" went up, I tried to cruise at the posted truck speed.
Only rarely did I override the cruise, say up a steep grade somewhere or to pass without holding up left lane speed-a-holics, or to engage the exhaust brake down a long hill. Normally we would stop in La Grande or Baker City to refuel and eat, and I normally have 1/2 tank at that half-way mark. I was flabbergasted as we reached Pendleton and then Meacham, and my guage and Alladin indicated I was no where near down to a half tank. In fact, I didn't hit that point until around the air base at Mountain Home, east of Boise. The Idaho section required a bump up in speed to be safe, due to the higher posted limits. Nevertheless, it was an awakening when I finally filled the tank in Twin Falls, and calculated 9.6 mpg. Keep in mind that this CAT had only 8000 miles on it at the time. Imagine the numbers when it gets broken in.
In dozens of identical trips over the decades, in cars and our old gas motor home, it took at least 9 hours, which included rest stops, refueling, and meal stops. I was so comfortable on this trip, that I drove the entire way non-stop. 8 hours. My take is that at the moderate speeds I never got stressed, and could even actually enjoy the country as we went by. I've always found that hard to do at 65-70 mph. The comfortable ride probably helped, as did no work for my right foot. I could have switched driving with the Missus, but was never tired until a half hour after we got past Boise's more stressful freeway section and darkness fell.
The cruise control is probably the number one contributor to the good mileage - set it and pretty much forget it, except the occasional exhaust brake or manual shift on hills or to pass. Minimize the amount of time your foot is on the throttle or brake. Secondly, be patient and enjoy the trip, even if its one you've taken dozens of times. Stay at or just above the posted truck speed; 65 to 75 mph may be normal in Texas, Wyoming, or Montana, etc., but if you're serious about minimizing fuel use, for yourself and for the country's sake, then make the conscious, deliberate decision to slow down. Our most enjoyable trips are on good state and county "backroads" at 40-45 mph. Anything over 60 on a freeway with all the nuts is hardly enjoyable. Or fuel efficient.
-Joel
Sorry Ted- we kinda got off-topic. :-/