If you run 4A on bare road the front axle is spinning and sucking fuel. Run it in 2H when the roads clear, then use 4A when the snow shows up if it ever does.
in my experience, i have seen zero difference in fuel consumption after extensive highly varied driving in normal mode 2H or normal mode 4A, for comparison purposes.
if there is a mpg difference, it's not showing up with any significance on my repeated actual per-gallon maths 90% of the time from the exact same station / same pump / same octane, for the entire pandemic basically....
(not sure if it makes any difference that i've got the 4wd / 3.31)
i did not really believe it at first, until i methodically tried it for both long trips & local city driving as well, just to make sure i was actually getting the same results in either mode & in all conditions. i know the front axle is spinning in 4a of course, so there is obviously the potential for extra wear, but i have a warranty for another 8 years & 100k more miles, so i don't really care about that so much - so far i've got about 10k running in 4A daily & no issues on the front end have appeared yet, currently @ 50k.
who knows maybe i'll eat my words in short order, call me crazy but i *always* run mine in 4A because the front end steering tightens up significantly & i prefer the way the truck handles on our back country roads - plus i usually have to to actively evade to avoid a deer at least once a week, sometimes in pretty extreme cornering & ending up damned near sideways, so i would rather have the truck in 4A in general just in case i started to lose any traction for any reason, wet, dry, wildlife, whatever...
i'm sure i'll get flak for it - but in short i've not been able to show any MPG difference between them & i love leaving it on 4A - all. the. time. (until something breaks & i come back here complaining about being stuck in an escape while they source parts...)