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Tow Haul = +mpg ?

zibzer

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zibzer Enthusiast

zibzer

Posted
Posted

I drive to work nearly every day and its a 22 mile drive and I have a MPG meter that consistently tells me I get 20.1mpg give or take 1 mpg

today I started driving home and thought I would put on tow/haul the whole trip just to see how bad it effects gas mileage. Well I was in a huge surprise, driving down the highway I noticed the MPG readout to by better than normal. plus I never dropped gears going up hills and MPG stayed high on the hills. when i got home I clicked the average button on the MPG readout and was surprised to see 21.98MPG for the trip, nearly 2mpg better than normal. (basically it stuck in 3rd gear the whole way home)

 

Has anybody else seen this before? This is the first time ive done this so it could be a fluke, but im going to do it again next time i go to work and see if it stays consistently good MPG.

 

Truck specs:

2000 Chevy Silverado

4.3L V6

slightly bigger tires

(dont know the differential size)

 

Im thinking the gearing is probably 3.6ish and I bet if I was to replace it with the 4.10 I would get better mileage due to less work of the engine.... at least according to my first test by driving in 3rd (tow/haul)

 

 

ANyone have any opinions or similar experiences??

snarkee Senior Enthusiast

snarkee

Posted
Posted

when i have a box full of gear and a 3000lbs trailer, I notice that I get better mpg in tow haul mode then regular mode....I found in tow mode it drops to 4cyl more often than regular mode

Joe28443 Enthusiast

Joe28443

Posted
Posted

I found that I get near the same MPG towing my 6500# camper. I get a little better than 14 not towing and between 10-11 towing in 3rd with the tow haul. Although I do live in a busy town and have to start and stop alot that probably explains my 14 MPG :lol:

TexasAl Enthusiast

TexasAl

Posted
Posted

This is interesting. Was your commute mostly highway or in town? I am tempted to try this, but my 50 mile commute round trip is on the highway going 70 mph. The truck should be fine, I guess. I will try it out today on the way home.

 

-al

gvbhunt Enthusiast

gvbhunt

Posted
Posted
when i have a box full of gear and a 3000lbs trailer, I notice that I get better mpg in tow haul mode then regular mode....I found in tow mode it drops to 4cyl more often than regular mode

In Tow/Haul it actually goes into 4cyl mode in 3rd gear. In regular mode if you put it in 3rd, it will not engage. So as long as you are going faster than 40 and slower than 60 you can be in 3rd AND in 4cyl mode. Pretty nice if you are places where the speed limit is 45-55. You can almost stay in 4cyl constantly due to the gearing.

maka Enthusiast

maka

Posted
Posted

my tow haul enables my truck to rev higher which leads to worser milage on my 4.8

rogg5204 Enthusiast

rogg5204

Posted
Posted

Hmm... This is strange. Let's see if I understand this right; When you put it in TOW/HAUL mode, it switches to 4cyl mode more often. This is the opposite of what I would expect. I would think that when you put it in TOW/HAUL mode, it would cancel the 4cyl mode because it would have been designed for use when power from all 8 cylinders is needed all of the time. Unless the computer is expecting the engine to be working hard and since it doesn't detect anything close to what it should for TOW/HAUL mode, it just drops it into 4cyl. This probably doesn't make any sense, but this is the only reason I can see for this switch to 4cyl in TOW/HAUL mode.

gvbhunt Enthusiast

gvbhunt

Posted
Posted

In standard driving you can be in 4th gear at probably 20 mph. In Tow/Haul the earliest it shifts from 1st is 20, 2nd is 40, 3rd is 60. This mode was designed to allow the engine to stay in a lower gear making use of the added torque multiplier of the lower gear instead of making the engine work harder (and generate more tranny heat) by using a higher gear. The AFM (active fuel management) does not care if it is in either mode, just as long as the selector is in drive and the load on the engine is below a certain threshold (and a few other parameters like minimum speed, minimum engine temp, vaccuum, sunspot location, etc...)

TexasAl Enthusiast

TexasAl

Posted
Posted
In standard driving you can be in 4th gear at probably 20 mph. In Tow/Haul the earliest it shifts from 1st is 20, 2nd is 40, 3rd is 60. This mode was designed to allow the engine to stay in a lower gear making use of the added torque multiplier of the lower gear instead of making the engine work harder (and generate more tranny heat) by using a higher gear. The AFM (active fuel management) does not care if it is in either mode, just as long as the selector is in drive and the load on the engine is below a certain threshold (and a few other parameters like minimum speed, minimum engine temp, vaccuum, sunspot location, etc...)

 

 

Good point.

gvbhunt Enthusiast

gvbhunt

Posted
Posted

Another reason you get a little better MPG (driving below 60) in tow/haul is that in some gears (1st, 2nd, and I think even 3rd) when you let off of the accelerator, the tranny will Free Spool (watch the tach drop to idle even when you are doing 40). No engine drag=better MPG while coasting.

slomo007 Enthusiast

slomo007

Posted
Posted

Now if only we could set the truck to default to tow/haul mode everytime unless you switch it back. Tow/haul during the week going to work, non tow/haul on the weekends.

 

Interesting thread, I'll start giving it a try.

gvbhunt Enthusiast

gvbhunt

Posted
Posted
won't using tow/haul on a daily basis when not actually needed cause excessive wear or hurt anything?

Shouldn't cause any additional wear. I think that the only way that you could hurt it is to not let the engine catch back up if you are rolling and the tranny is free-spooling. Idle to 3k rpm only to slam into 2nd gear sure freaks the kid out next to you but it is probably not too good for it... Just give it a bit of gas to let it catch back up and then when it does drive it like you normally would. Hope the free-spooling makes sense. If it does not, put it in tow/haul and drive on a road where the speed limit is 35. You will immediately know what I mean.

Huntervh Enthusiast

Huntervh

Posted
Posted

Used Tow/Haul (about 250 miles round trip) a few weeks ago while towing a trailer with a snowmobile on it, did not notice any MPG improvement. But I did notice that when I switched to tow/Haul mode, my transmission temp went up about 10 degrees, this was about 50 miles into the trip that I turned on the tow/haul mode.

 

On the way back tow/haul was already on, when I got close to home I turned it off, no transmission temp difference.

 

Just a fluke, I do not know. Will have to give it another try some time.

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