Join Date: Nov 2005
Location: Memphis TN
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What's the rear-end ratio? Makes a difference. Also, the 80+ doesn't help. A close friend has an F250 with the 3.73 gears, and 2000 RPM on his is just a tad over 70. Your best milage is going to happen when you keep the RPM's below 2000 (that is your peak torque RPM). Larger diameter tires are going to hurt as it makes the engine work harder to get you to speed and harder work = more fuel needed. They also have an impact on performance. Ideally, if you go to larger diameter tires, you need to lower the gear ratio to compensate for them ... the down side, now you just lowered the speed at which you can run at 2000 RPM.
A steady foot and where possible, cruise control really helps. Example: just finished up a 3000 mile vacation pulling my FW. Left Memphis, spent a few days just north of Hope AR (Crater of Diamonds State Park), next on to Austin TX for a few days, then back home to trim the 'forrest' that is normally called grass, then to Gatlinburg TN for a few days then back home. Experienced everything from flat country to 5% grades and averaged 11.7 for the trip ... tried to keep my speed between 60 and 65 (with the tow boss 61MPH is 2000RPM). Decent milage is possible ... I say decent as I think 11MPG dragging an almost 14K of trailer around is decent.
2006 F350 King Ranch CC DRW 6.0PSD TorqueShift
Dk. Copper / Tow Command / Tow Boss
Power Slider / Power Pedal Adjust
OEM Bed Liner / SportsMaster Rollup Tonneau
15K Fifth Wheel Hitch
2006 Keystone Everest 345S Fifth Wheel