I've noticed this since I took ownership of my 2016 3.5. The DTE counter seems to have big swings. This example has happened a few times at various readings. Get in cold truck the DTE reads 419. Travel two miles down the road/highway at a constant speed let's say 65 and staying out of boost. The truck jumps from 419 to 412 within those two miles. Truck wasn't parked on a hill or anyplace where gas tank position would make a difference. This has happened a dozen or so times on my truck.

 

7 mile DTE change with a full tank isn't a large swing. On a 26 gallon tank that is the difference between 16.16mpg & 15.86mpg. Are you reseting your fuel mileage deal? It's going to make your DTE swing more until it's got some mileage history on it.

 

Happens to mine too but more than that, ive seen it fluctuate 80 ish kms sometimes.

 

Twice during a 4000 mile round trip, while cruising at 65 to 70 mph, my dte showed 800 miles at fillup. I drove a couple of blocks to the hotel for the night. The hotel was only a couple of blocks from the on ramp for the interstate and 75 mph speed limit.

When I set the cruise at 80 mph, with a cold engine the dte had already dropped so much I thought someone had stollen fuel from me. But the gauge still showed full. By the time the engine was a full operating temperature, the dte was down to almost 700.

 

There was an updated post a few days ago that talked about how the calculations actually calculate.
Sort of interesting, but nothing mind blowing. Bottom line, it will hunt for DTE and be reasonably accurate, but not so much you should plan your next stop by it once it gets low.
Calculations were something to the effect of calculating the previous 30 miles, or something like that.

 

Myself i go by the fuel gauge when its time to fill up and ignore the DTE reading which i seldom to never look at.
I never let the tank go below somewhere between 1/8 to 1/4 full.
The DTE IMO is little more than a bell & whistle 'ball park' gimmick meaning the computer formula to calculate it has to factor in the real time current fuel mileage which can vary a lot depending on driving habits, etc.

 

Perhaps I'm missing something but I've noticed the DTE is not in sync with the odometer. I'll have to watch it again. I might be comparing 1/10ths to miles if it's displaying tenths in that display..

 

Yep, see my post just above yours.
It's calculated off of a previous average, not a current average.
I continually see a drop in miles for DTE than miles I've since covered.