I drove the GS B touring above from Dallas to Grand Canyon and back for a total of 2100 miles. Truck has only 2200 miles on it at the beginning of the trip. I had dumped the Ford semi sythetic oil before the trip and put in Mobil one 5w30 full sythetic with a new mortorcraft filter. Driving only 66 mph, elevation change from 600ft to 7000 ft. and back, and slightly over inflated tires (69 rear and 79 front) it got 11.7 mpg. No too bad I would say. All worked good.
No I was not towing, was with one other person, and fresh tank and both holding tanks empty. I assume you have the older ford v10 6.8L. It is a good engine but yes it only gets about 8 mpg. The new 7.3 V8 gets about 20 to 25 percent better MPG from what I have seen. Hope it stays that way! I did have tail winds most of the time also.
Ya tailwind makes a difference for me in noise, mileage is negligible. I would assume you have the 10 speed transmission which would keep the engine in the best power economy range.
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Jim Zapp
08 BTouring cruiser 5290
07 Ford cutaway chassi
Nope. Still the six speed. Racking out at 2400 rpm on the road. And the 10 speed would not have helped a bit, for I am told the 10 th gear is the exact same ratio as the 6th gear in mine. U got 10 gears in newer light weight trucks to save gas around town but it’s negligible This 4.56 ratio rear end dictates these higher rpms on the highway. I think about a 4:10 with only being 10k pounds rig would be maybe a better fit, however I loved not one down shift going up hills if it was above 60 mph!