I just bought a 2018 F250 with the 6.7 and I have a question about the shift pattern. My 2017 with the same motor gets about 19-20 mpg running 65 or so (until the DEF system kicks in). On the same trip my 2018 gets a lot less mpg and I noticed that it shifts at higher RPMs than the 2017. The gearing in both is 3.55 and I can see they run the same RPM in 6th gear at the same speed. The only difference is that where my 2017 shifts at 2k RPM the 2018 will run up to almost 3k before shifting with the same type driving and acceleration. The 2018 was used to haul a 5th wheel and also has the heavy duty rear suspension. My questions are (1) were there multiple transmissions available so the 2017 and 2018 might have different transmissions and shift differently and (2) do these trucks develop any pattern after use so that the 2018 after towing a heavy 5th wheel for the 43k miles of its life shifts differently than the same truck that has never really towed anything? It almost feels like the tow/haul is on all of the time but it is not engaged. I know the specs changed a little from 2017 to 2018 but 10 hp shouldn't cause such a change in mpg between two trucks that are basically identical.

 

I believe what you are referring to is called shift scheduling.

On some vehicles that is learned and adapts to how the vehicle is driven.

What influences shift points is usually inputs to the trans and powertrain modules. If the scheduling is lost for whatever reason , new shift points are relearned.

If the battery is disconnected and some memory is lost, , if the vehicle is driven normally it will relearn those shift points.
You might consider that.

 

Ok thanks. I will disconnect the batteries and let it sit for a while and see if that changes anything.

 

Generally shift firmness Up/Down changes with KAM removed, and overall strategy changes a bit until the learn adjusts. But 1000 RPM in shift strategy at the same throttle angle and conditions? Did the truck you just bought receive (depending on State/Location) Emission Recall 20E07- ?
My 2017 6,7 fuel mileage is about the same as yours out on the open road unloaded. Shift point of course change with throttle angle, certainly with TH applied but generally aren't much over 2Kish under light conditions . Just curious if your truck has had the latest PCM emission programming (?) Not sure what drivabilty/strategy it would change, and its not addressed as far as I can tell. At a guess, I'd say it will diminish mileage at the very least