Welcome to the asylum..
Are you refering to the DTE number?
On the OEM Michelins, no FE air brake/noise generator on the roof, driving 60-63 on the interstate on cruise control, ECO mode, after filling up with 93 octane ethanol free fuel, I recently drove from Cherokee NC to Brunswick Georgia, non stop, ~400 miles, and got 31.2 MPG on the dash (31.0 calculated at the pump) to a Buc-ee’s where I filled up with 90 octane Ethanol Free, and got a brisket sammich for supper.
The dash showed 427 miles DTE. Somewhere, I have pictures to show that, I’m not going to go hunting for them now. I don’t care if you believe me or not.
On the return trip, on the exact same route, same speeds, using 90 octane Ethanol Free fuel, I only got 28.5 MPG. I have noticed this in the past with less than 93 octane E-0 fuel. Wind direction, octane rating, and elevation change (1650 ft to sea level) were the only things that changed on the two trips.
Since I have recently been driving locally more, my calculated tank averages have dropped to 26-28 mpg, from 28 to 29mpg, and as low as 21 mpg, as has my DTE value. Two nights ago on the way home from the Drive Inn theater, after filling up with 93 octane E-0, my DTE was only 401 miles.
With ~40,000 miles on the OEM Michelins ATX’s, I recently put Bridgestone Dueler AT Ascents (OEM size) on Miss Daisy, after that trip to Jekyl Island, and despite the Duelers being very near to the weight of the OEM Michelins, I seem to have taken a 2-3 MPG hit on fuel economy, across the board. They are quiet, and seem to have a great ride. I am still hunting for the best inflation pressure for the Duelers. I started at 33 PSI (nitrogen fill at Costco), then went to 34 PSA (nitrogen), then 37 PSI(nitrogen). Now I will start back down, only when on long road trips, where Miss Daisy gets her best MPG. Time will tell how much of a MPG hit I took going to the Duelers.
Good luck.