Gas mileage in tow mode or not

[BessieB]

The other day coming home, my hubby didn't fill up the tank to come over the mountains. So needless to say, we whistled into the gas station. He took the transmission out of tow mode cause he thought the truck gets better gas mileage that way. Is he correct in that? I would think it wouldn't be helpful to the transmission to be towing a trailer and not being in the tow mode.
Thanx for educating me please.

[SteveH]

The answer to this, I think, is like many subjects, it depends. With my tow vehicle if I don't drive fast enough to get into sixth gear in tow/haul, I get worse fuel mileage, but if I do go fast enough (about 65-67MPH), I get the same fuel mileage.

I have friends that report they get better fuel mileage out of T/H, but they also report they never go over 55.

The T/H mode is there to actually protect the transmission from overheating, and lets the engine run at RPM's that are more efficent when under load.

EDIT: My TV is a 3/4 ton Diesel GMC, and my trailer is a 31' Classic wide body.

[tkasten]

I have checked it both ways. Same mpg. The big difference is that the tranny runs much cooler in TH mode. What that means at highway speeds 63 - 65 is it's running in 5th not 6th which is overdrive. Just my experience. Much depends on how much weight you are hauling and what type of engine. Mine is a 5.3 V8 w/6 speed.

[Tim A.]

A cooler transmission might help it to last longer. Any small savings in fuel cost from not using tow/haul, with the possibility of overheating the transmission, would probably not pay for the cost of a transmission overhaul or, horrors, replacement..

Tim

[Minno]

With our 2009 Dodge 1500, tow haul mode (we always call it toy haul mode ) inserts an extra gear into use that is not available when out of tow haul mode. At 60 mph, weather in tow haul or not, we run in 5th gear. The extra gear is either 3rd or 4th, I forget which to be honest. It also changes the spark advance in the hemi engine, and we do notice a difference accelerating while in tow haul mode when we have the trailer in tow. It gets up to speed faster while in tow haul mode.

Our Excursion was much different. There was an overdrive off switch that we used when towing in mountains. Other than that, we never turned off overdrive, as the trailer we had at the time was only about ½ the tow capacity of that beast of a truck, and the tranny never hunted between gears.

It really does depend on what truck you have, what tow haul actually does, and how much weight you’re towing.

Chris

[Gene]

Originally Posted by SteveH

The answer to this, I think, is like many subjects, it depends.

Yes.

My understanding is that it changes the shifting points so the transmission stays in the lower gears longer so as not to strain the engine. Going downhill it may make the transmission downshift sooner and save some braking.

I have no reason not to believe it also keeps the transmission cooler, but it may depend on which transmission, whether there's a transmission oil cooler, and whether the oil cooler works well. Our transmission oil temp gauge hardly ever budges even going up steep grades really fast, so I guess the cooler is a very good one (or the gauge is broken).

I use tow/haul because it makes sense to me to change the computer programming (that's what the button does) for heavier loads. I have never noticed any change in gas mileage. Gas may be expensive, but engines and transmission are much more so.

Gene

[StreamRollin]

I am posting on this thread so Jim reads it (we share StreamRollin) ... he was wondering the same thing about gas mileage and whether or not to take it out of tow haul mode on flat land or non-incline roads to save fuel. We also have a RAM 1500 v8. Good info, thank you! Wendy

[BigAl]

In the guide book for my 2011 ford Ecoboost engine it states to use tow/haul if the transmission starts to hunt for gears(shifts often). If not then in normal drive you will get better gas mileage.
I haven't towed in the mountains with it but in Ontario, Canada and the northern states I have not had any reason to use tow/haul. And I bought the truck just for that option. I tow a 31 foot Airstream in sixth gear at 55 mph at 1500rpm and it is effortless. The transmission does not unlock and rev up in sixth gear, but downshifts if the load increases on a hill.
At that speed my gas mileage is about 13.5 to 14 mpg(us) depending on hills.
I am amazed with that fuel economy.
If I tow at 60 mph the fuel economy drops to 12.
Al

[purman]

Originally Posted by CrawfordGene

Yes.

My understanding is that it changes the shifting points so the transmission stays in the lower gears longer so as not to strain the engine. Going downhill it may make the transmission downshift sooner and save some braking.

I have no reason not to believe it also keeps the transmission cooler, but it may depend on which transmission, whether there's a transmission oil cooler, and whether the oil cooler works well. Our transmission oil temp gauge hardly ever budges even going up steep grades really fast, so I guess the cooler is a very good one (or the gauge is broken).

I use tow/haul because it makes sense to me to change the computer programming (that's what the button does) for heavier loads. I have never noticed any change in gas mileage. Gas may be expensive, but engines and transmission are much more so.

Gene

I have been reluctant to use it as our gage doesn't change whether towing or not, like you say. Guess they both must be broken. Toyota thing

I figured it just changed the shift point and have never felt i needed to it shifts fine when towing in normal mode.

I keep it on our 4-runner because it lags going up the 2000 ft elevation from work.. 5000 ft to 7000 ft in 15 min 13 miles of driving, but have no problems with the Sequoia. I will have to give it a try this summer on our trip to Oregon to see if there is any difference over the mountains and on the flats.

[dznf0g]

Gene is correct, at least for GM.
Tow/Haul mode raises shift points, will downshift sooner on decel for engine braking, increase line and apply pressures and will hold the trans out of high gear longer to reduce shift business....however it does not "lock out" overdrive.

It is recommended to use TH mode if your trailer weight is at or above 75% of the rated trailer weight for the particular TV.

It probably does hurt fuel economy a little, but will help performance as well as transmission durability.

But, again, it is not necessary unless your trailer weight is at least 75% of rated capacity. The manuals really don't address GCWR, but I believe the 75% rule is applicable to that number as well, if you carry heavy bed loads and a smaller trailer.

[BessieB]

Thanx all for your replies. I will pass it on to hubby. We have a Chevy Silverado HD 1500. Our trailer is 22' or 21'. Whatever there. So since we are in mountain country, that engine does get a workout for sure.

[ROBERT CROSS]

Originally Posted by BessieB

Thanx all for your replies. I will pass it on to hubby. We have a Chevy Silverado HD 1500. Our trailer is 22' or 21'. Whatever there. So since we are in mountain country, that engine does get a workout for sure.

IMHO....A 1500 Silverado deserves to be in T/H in all but the flattest conditions.
Kansas...maybe not so much.

In the mountains, you might consider an auxiliary transmission cooler. Ck Amazon for pricing.

Bob

[dznf0g]

Originally Posted by ROBERT CROSS

IMHO....A 1500 Silverado deserves to be in T/H in all but the flattest conditions.
Kansas...maybe not so much.

In the mountains, you might consider an auxiliary transmission cooler. Ck Amazon for pricing.

Bob

I wouldn't go quite that far. I had a 22' SOB and didn't use TH hardly at all....but I do live in the flattest conditions. Last summer I got out my 10' step ladder so I could see over the corn, and lo and behold, 700 miles to the west I could see the Rockies.

Really, though, even when I overload a 1500 with my 30' Classic, with a tailwind, I can get away without using TH mode. BUT, again.....it's really flat 'round here!

[BessieB]

Our trusted mechanics said our truck could handle a trailer. I even asked how big we could go. They said no problema. Now I know with our 2500 I wouldn't have had to ask. But alas, we clunkered it. I miss that truck.