I usually get 15-17 highway mpg with nothing in tow. If towing my 5th wheel, I usually get 8.5 mpg but today we had taken most of our stuff out of the camper as it went in for some warranty repair and I got 11 mpg (computer reading) while towing it to the dealer. I don't know how much weight we removed but that was shocking to me. I've never got anywhere near 22 mpg whether it be with my 6.4 Hemi or any other full size pick up truck I've owned. Not even when just putting along with nothing in tow. Your computer has to be wrong if that was your overall average. I will say that I've seen 99 mpg and 2 mpg on the computer during a trip but those aren't averages. Those were at that moment mpg readings.