2,250 mile roundtrip to Colorado. Started with 465 miles on the clock. Drive out yielded 17.6 - 17.8 mpg. All highway with mixed rolling hills and gradual elevation gain, averaging 75mph light loaded bed, single occupant. In mountain driving mixed highway and off-road, MPG's stayed in the 17's. With roughly 1,500 miles on the clock, the return trip saw as high as 20.7 mpg, gentle rolling hills and gradual decrease in elevation, speeds 75-80mph, 2x occupied, additional 200lbs of cargo. Bone stock '21 T.B. 5.3L with bed cover. Also things to note: Steering can be sensitive at these highway speeds. Small input, larger correction than I would expect. I have been driving for 30+ years and have clocked over 2,000,000 miles (non-CDL) during this time in various types of vehicles. The reactivity of the steering input is greater than I would expect based on my driving history/experiences. That being said, it's manageable once you get familiar with it. I wish it was user adjustable (maybe an electronic assist disable feature once hwy speeds are attained, or similar). Another thing to note, truck with modest load does very well at maintaining top gear/lockup at these speeds on decent hills, as opposed to my old Tacoma (2019 model with 6 speed Auto) that would shift 397 times up a hill and down the other side. That pissed me off every. single. time. I'm running a ScanGauge II and monitored ATF temp along with coolant. Happy to report that the onboard ATF reading displayed matches ScanGauge console. Yes, I know it's getting it's info from same sensor but there are instances of different numbers being displayed between the two in various vehicles. Ran about 143-148 degrees on the hwy at above mentioned speed. I did hit some dead-stop construction areas with 88-90 ambient temps, during this time the ATF got as hot as 165 degrees. Stop times were 5-10 minutes each. Recovery time for ATF temp when hwy speeds were re-attained was about 8-10 minutes. There was noticeable shift pattern changes with hotter ATF. The upshifts tended to take a second or two longer to occur. Expected, but notable. Could have been a variance in throttle position, but it was readily repeatable giving me the thought that it was temp related. Not a big deal, but notable. Also, downshifts (automatically controlled, no input from me) were a bit more mechanical (clunking) than with cooler ATF. Coolant got as high as 210 during these stops, but normally ran around 198 degrees. So far, impressed. Nothing sticks out as being problematic at this time.