I can show 40 miles to empty and only put 22 gals in my 26 gal tank. I usually don't let my tank go this far, but I was on a trip and wanted to see the range available. I was averaging 24 mpg figured at the pump, so that would be about a 2 gal or so reserve. My brother in law with a 2020 XLT with 0 miles to empty can only put 31 gals in his 36 gal.One of the things to consider with the 36 gallon tank, is it has a 5-ish gallon reserve. So the range is a bit disappointing compared with the smaller tank sizes.
My truck is currently showing 18 miles to empty but I know the tank has at least 5 gallons remaining.
Twice, I have filled up my 36 gallon tank with only 50 miles to empty shown and each time, the truck only took 26.3 gallons. I doubt that the 30 gallon tank has that same peculiarity.