MPG decrease AFTER a haul

Bugsplatt9 · Apr 5, 2016

Greetings all. I have noticed that after I have made a haul using the Tow/Haul function and have switched back to normal ops (without a trailer), I am getting a noticeable decrease in fuel economy. This seems to be the norm and it doesn't seem to matter how light or heavy the load was. Wondering if besides changing shift points, the T/H mode adjusts fuel/air mixture. Any thoughts?

chris1965 · Apr 5, 2016

how do you notice it? did you reset your display?
I always reset the trip counter A after every time I get gas- this shows you also the fuel mileage for the trip and not the total. there you see the real mileage. the main display shows you the over all as long as you don't reset it. if the fuel mileage does not go up right after tow, it takes a good while, till it is back to normal.
The real fuel mileage you can do the math, how far you went and how much gas you got. but for the thumb the display does it pretty good.

PippinAin'tEasy · Apr 5, 2016

Haven't checked mpg's but I know after a long run (couple of months or so) it'll jump off the line like a scalded dawg if there's no load. Still trying to figure the 'puter magic on these things myself.

"Oh, sweet debt. Thy name is Truck."

wasntamoparguy · Apr 5, 2016

probably adaptive learning. Adjusts shift points and pressure, throttle opening, etc to drive smoother. Honestly I wouldn't do anything just keep driving it and it will relearn how to drive over time.

Bugsplatt9 · Apr 6, 2016

This is discovered by resetting the display and observing the averages over the next several days. When I'm not towing, I leave the overall/combined computer alone in order to see a true average over many tanks of fuel, but I tend to monitor the realtime numbers while driving in order to modify driving habits for increased MPG.

I don't intend to do anything to it, just wanting to understand it. I'm on board with the adaptive learning theory, just wish it learned a bit faster and not a full tank later. Fuel is cheap right now, but I get a kick out of driving a big pickup that typically can get 21MPG combined with no other load than the topper.

On the other hand, I love the HEMI and you gotta cut 'er loose once in a while!

2015HD · Apr 6, 2016

I'm glad you posted this, I've noticed the same thing, it always seems to take a tank or two until I see the average go back up. During the winter when I have plow on and I use Tow / Haul or when I actually tow / haul something. I reset my trip A each time I fuel up. Last week I was averaging 14.5MPG in my 5.7 2500. On Saturday I hauled my camper and a very heavy load. I fueled up Monday and since then I'm averaging 13MPG. Sometimes it's actually a more substantial drop but my hauling on Saturday was only about 10 miles total, this seems to support the adaptive theory. Funny thing, I actually noticed the same issue with my 2104 Silverado. Damned computers :flipthebird:

MPG decrease AFTER a haul

Bugsplatt9

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chris1965

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PippinAin'tEasy

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wasntamoparguy

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Bugsplatt9

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2015HD

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