Settle an argument for me, please!

Thank you all for the replies. It kind of reaffirms what I thought about it and been doing all along towing with different vehicles.

tell him to pull less weight to get better mpg! lol :) T/H all the way.. save the trans...

I think it depends solely on how you drive. Since it will hold the lower gears longer, if you're easy on the pedal, you might do better by not lugging the engine.
Higher rpms do not necessarily mean lower mpg if you're lugging the engine in a higher gear.
IMO, the difference is too trivial to squabble over.
I say if you prefer to drive in T/H, go for it.

Are you sure your buddy is not confusing tow/haul mode with the OD switch. The OD switch pretty much just prevented your tranny from going into OD, creating higher RPM's and bad fuel economy yet needed when pulling heavy loads. This was all back when trannys did not have all the electronic stuff that they have in them today. If he is thinking about the OD feature then he would be correct.

Now with the electronically controlled tranny's the tow/haul mode switch came out and operates completely different than the OD switch ever did. Others here have posted how this works and I don't think the switch affects mpg that much. Just use it when needed to get the best life and fuel economy for your RV.

As far as the post above with the Ford and the OD being disabled when in tow mode, not sure about that. I have a 2011 Jeep GC, 2010 Dodge Ram Cummins and my 2011 Ford Class A. None of these vehicles disable OD with the Tow/Haul mode switch on.

ferndaleflyer wrote:
I have 2 Fords and if in OD and hit the TH button going say 60mph it will shift out of over drive and the rpm will increase. I would assume that more RPM means less fuel mileage.....could be the reason it gets 17mpg without the TH engaged and 15mpg when it is.....Am I wrong or is there some other reason the mpg changed. This was on a 350 mile each way trip towing nothing.

No you are not wrong, however tow/haul mode means different things to different transmissions. In your specific case, it locks out overdrive, as your truck is geared to purr along at a super low RPM, to get better mileage. An RV is not geared that low to begin with, so tow/haul mode doesn't need to shift out of overdrive, however it does change the shift points.

There probably is a cruising speed that tow/haul mode would cause it to downshift, but apparently not at the speed the OP drives. SO the only negative is the increased pump pressure, which does hurt the mileage, but not by enough to easily prove it. (That is why everyone keeps saying it won't change it, even though it will, by a very small amount)

I have 2 Fords and if in OD and hit the TH button going say 60mph it will shift out of over drive and the rpm will increase. I would assume that more RPM means less fuel mileage.....could be the reason it gets 17mpg without the TH engaged and 15mpg when it is.....Am I wrong or is there some other reason the mpg changed. This was on a 350 mile each way trip towing nothing.

KD4UPL wrote:
IF it hurts MPG it would be so small as to be nearly undetectable.
At cruising speed the torque converter would be locked whether in T/H or not. The RPMs would be the same. The shift points wouldn't matter because it's not shifting.
When stopping, starting, accelerating, etc. T/H off may give the mentioned nearly undetectable increase but that's not the point. T/H mode is the proper mode according to the designer of the vehicle for the situation. It provides better acceleration/deceleration and less mechanical wear on the vehicle. I wouldn't sacrifice vehicle control and longevity for .1 MPG.

described perfectly!!!

Any added weight will hurt mpgs to a small amount. Perhaps barely measurable.... Not worth getting in an argument about. :)

wny_pat wrote:
Using A Transmission with Tow/Haul Ignore the "Ignoring the Barking Dogs" article and skip right down to the towhaul article.

With the Duramax I used to just click it off and get in into 6th gear and then click the TH back on and it stayed in 6th gear. You can always speed up a little to get it into 6th and then back right down. I can't imagine that it would do much for mpgs. I do know that with the Duramax/Allison, the tranny would run a little cooler with the TH on when I towed my Montana 3474RL. I'm suspect the same with the TorqShift. I have done mostly all mountain driving so far and i'm getting a little over 6MPGs. Mountains are rough on MPGs!

Using A Transmission with Tow/Haul Ignore the "Ignoring the Barking Dogs" article and skip right down to the towhaul article.