30 mpg is absolutely possible. This pick of my 4th gen mileage (Pentastar v6, no eTorque) earlier this week. Went from Martinsburg, WV to West Point, NY for my niece’s graduation. Had a couple hundred pounds of cargo, me and my wife. Cruise set to 65-70.
Instant computer read outs don't count. Hand calculations only.
I have that same 3.6 in my Jeep with a really really tall last gear (think my rear end is 3.09 or something horrid like that). Best I can get, in a smaller/lighter Jeep with the same engine, is about 26 mpg, hand calculated, coming down the Canadian shield, with a gas pump literally on each end of the trip and also literally only 1 acceleration from 0 to 110 KM/h with the rest being just maintaining speed. No cruise control (that worsens your MPG, BTW), just feathering the pedal and strolling along in the right lane.
It was just me in the Jeep, and I was lightly loaded. The trip was 2 hours and 45 mins. I do have AT tires (Cooper AT3) but shouldn't do much damage.
But we're talking Toyota here; their current trucks are the worst in the industry for MPG. They're not going to manage going from 15 MPG to 30 MPG in one generation.