[MikeD1]

The DTE is calculated by using the current MPG as a factor, so with the MPG being down the DTE will go down as well.

Is the MPG accurate ? Have you manually calculated the MPG for a few gas stops? Fuel gauge seem to be reading correctly?

 

[MikeD1]

Okay. The DTE in its relationship to the MPG makes sense. And my fuel gauge seems to be working just fine.

I guess it just comes down to the difference in the MPG that I'm getting.

Why the big difference in the MPG when I'm driving no differently than I was before?

Having lived in Mich for 30+ years, I can assure you you are driving differently this time of year + the winter fuel blend = crappy MPG !
Because of the cold & snow, it's taking longer for the engine to get to operating temp & you're spending more time in stop & go traffic. Add to that if you start the car & let it warm up a bit while cleaning off the windows or the inside temp warms, all + a significant drop.

These D's seem to eat a lot of gas at idle, I've noticed my MPG drops if I sit idling with the a/c on here in FL, even 10 minutes makes it drop.