Improved Mileage When Towing

[GlennSullivan]

2017 4x4 Expedition 3.5 V6 3:31 open differential and HD Tow option. We tow 3 or 4 times a year. 2 of the trips are 1240 plus miles. Always use premium (93) when towing and don't use tow haul mode as I don't like the way it is programmed to use engine braking (drop gears) when descending hills. Typical mileage on these long runs with 1600lb trailer and 3400lb car (5000TTL) is 13.3-13.5 mpg.

On a long trip last fall, I started locking out 6th gear in hilly areas and the mileage improved. This spring on the return long haul trip, I decided to keep 6th locked out the entire trip. The results were very pleasantly surprising.

 

[callwill]

does tow haul stop the torque convertor from locking up?

 

[GlennSullivan]

I don’t believe it does on the 2017, however the tow / haul settings as well as most of the transmission programming between the Gen3A / 2010 to 2014 5.4 3 Valve NA and the Gen 3B / 2015 to 2017 3.5 4 Valve TT are day and night. I currently own a 2011 and 2017 and can confirm this.

 

[Utah Driver]

Yeah, I don't like the downshifts in tow mode. Just FYI, the 6R80 has two over drives. My 16 has a 3.73 ratio. According to the internetz, the tow/ haul affects the longevity of clutch packs.
Key Features of 6R80 Tow/Haul ModeRevised Shift Points: The transmission holds lower gears longer, keeping the engine in a higher RPM range to maximize torque and power when accelerating, reducing "gear hunting".Engine Braking (Grade Descent): When slowing down or descending hills, the transmission automatically downshifts to increase compression braking, reducing strain on the truck's service brakes.Firmer Shifts: Increases transmission line pressure, which makes gear shifts firmer and reduces slippage/heat in the clutch packs, increasing longevity.Torque Converter Lockup: The torque converter locks up earlier and more often in gears 3 through 6 to reduce transmission heat and improve fuel efficiency.