MULV, I am withyou on the F-150,
best I did with mine was 16.5, combo of city and hiway,
but I had to do some creative driving, i.e. neutral down hills, cut corners, etc.
I have on occasion rented a Durango on business trips,
bo did I have gas pump shock when I filled it and
I did not drive that much.
You could just tell it did not get good milage.