let me add some soup to the bowl.
We have used 91 octane at each fill up since new, except for maybe one or two tank fulls.
reasoning is most of my driving is High speed (70 or higher, mostly higher).
second is the summers are freaking hot and i demand alot from my vehicles, cold as snow a/c and no hiccups.
whether the 91 gets me better mpg over 87 is anyone guess.
I will say i have done a few fill-ups with NO ethanol 91 octane. YES in short order its a different feeling, but this fuel is pricey, nearly 75 cents more per gallon than 91 octane that may contain some ethanol (10%).
i see on here at least one other person after a year are within .1 of my lifetime mileage of 17.3.
and that is in 2wd or 4auto mode. I have found no mpg decrease when having the auto 4wd system in auto, just makes more noise up front. But in rainy or potential reduced traction on roads, i use the 4wd auto setting.
traction control, you can turn it off, but somewhere over 35 mph its back on and cannot be kept turned off, despite the settings in the menu. should get a flashing light to let you know its back on, but i cant remember the mph settings. that is unless your in 4wd High mode, which is not suitable for dry pavement operations.
4wd auto may be used on all surfaces, but not recommended in mud, snow or low traction conditions