I have been towing our 30ft fiver for years with a Silverado 2500 Duramax. Have been using the tow mode and get right around 12MPG. Today we headed out. I zeroed out the trip computer before leaving. Stopped at a rest area about 100 miles out, all freeway traveling at about 60 as usual. It’s then I noticed I had forgot to put it in tow mode. Checked MPG reading and was surprised to see 15 MPG. Tran temp and engine temp were normal so just left it off the rest of trip, another 140 miles. Checked again at end and got 14.4 MPG. So my question.. On fairly flat highways should I leave towing mode off and only turn it on when I hit the hills?

The main thing to remember is that the MPG reading is a lie. If you really want to know your MPG, keep track of mileage and amounts added to the tank, over several tankfuls you'll get your pretty accurate MPG.

The tow mode does not have much effect when towing on flat roads at crusing speeds. It makes the engine rev more when starting from a stop (which uses a bit more fuel), and it causes the transmission to downshift when you apply the brakes on a downhill grade. But you knew that, of course. I wonder, were you were towing with a tailwind? I have noticed a huge difference between towing into a wind and towing with the wind behind. I would not be suprised at the 3 mph difference if there was a good tailwind.

RoyF wrote:The tow mode does not have much effect when towing on flat roads at crusing speeds. It makes the engine rev more when starting from a stop (which uses a bit more fuel), and it causes the transmission to downshift when you apply the brakes on a downhill grade. But you knew that, of course. On older Ford vehicles, "tow mode" disables the 4th speed, which has a big impact on fuel economy.If you are towing on a flat road and the engine and trans temp stay in the "normal" range, don't bother with "tow mode". Be prepared to manual engage "tow mode" when you encounter any hills.This worked for me for many years with my E150, admittedly towing a smaller trailer.

fj12ryder wrote:The main thing to remember is that the MPG reading is a lie. If you really want to know your MPG, keep track of mileage and amounts added to the tank, over several tankfuls you'll get your pretty accurate MPG. Yes I have done that on long trips and found the computer to be maybe .5 MPG off.

On flat roads Tow/Haul mode really makes little difference. In hilly areas, it keeps it in lower gears longer (or sooner if it is downshifting) for more torque to pull up the hills (or slow down going down the hills). Translation: less shifting of gears.Since what causes the transmission to heat up is the unlocked torque converter during shifting, the tow haul mode significantly reduces transmission heat in hilly areas because it shifts gears many fewer times.If you don't want to use Tow/Haul mode all of the time, at least use it in hilly areas.

Have I been doing it wrong all these years? | Good Sam Community

BarabooBob
Explorer III
Aug 03, 2019
With my F150 the biggest advantage I see for using T/H is when going downhill with the cruise control on. It shift to lower gears faster to keep the speed form building up. On several hills around here the truck will shift down to 3rd gear to keep the speed at 55 mph (the speed limit.)
dodge_guy
Explorer II
Aug 03, 2019
TH doesn't care about flat ground. What it does is hold each gear longer when accelerating. When it's off it short shifts and can make the engine work harder building rpm back up which actually uses more fuel. I'm guessing you had a tail wind?
Bobbo
Explorer II
Aug 03, 2019
On flat roads Tow/Haul mode really makes little difference. In hilly areas, it keeps it in lower gears longer (or sooner if it is downshifting) for more torque to pull up the hills (or slow down going down the hills). Translation: less shifting of gears.

Since what causes the transmission to heat up is the unlocked torque converter during shifting, the tow haul mode significantly reduces transmission heat in hilly areas because it shifts gears many fewer times.

If you don't want to use Tow/Haul mode all of the time, at least use it in hilly areas.
rollexx
Explorer
Aug 03, 2019
fj12ryder wrote:
The main thing to remember is that the MPG reading is a lie. If you really want to know your MPG, keep track of mileage and amounts added to the tank, over several tankfuls you'll get your pretty accurate MPG.

Yes I have done that on long trips and found the computer to be maybe .5 MPG off.
theoldwizard1
Explorer II
Aug 03, 2019
RoyF wrote:
The tow mode does not have much effect when towing on flat roads at crusing speeds. It makes the engine rev more when starting from a stop (which uses a bit more fuel), and it causes the transmission to downshift when you apply the brakes on a downhill grade. But you knew that, of course.

On older Ford vehicles, "tow mode" disables the 4th speed, which has a big impact on fuel economy.

If you are towing on a flat road and the engine and trans temp stay in the "normal" range, don't bother with "tow mode". Be prepared to manual engage "tow mode" when you encounter any hills.

This worked for me for many years with my E150, admittedly towing a smaller trailer.
RoyF
Explorer
Aug 03, 2019
The tow mode does not have much effect when towing on flat roads at crusing speeds. It makes the engine rev more when starting from a stop (which uses a bit more fuel), and it causes the transmission to downshift when you apply the brakes on a downhill grade. But you knew that, of course.

I wonder, were you were towing with a tailwind? I have noticed a huge difference between towing into a wind and towing with the wind behind. I would not be suprised at the 3 mph difference if there was a good tailwind.
fj12ryder
Explorer III
Aug 03, 2019
The main thing to remember is that the MPG reading is a lie. If you really want to know your MPG, keep track of mileage and amounts added to the tank, over several tankfuls you'll get your pretty accurate MPG.

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