[TGCOFTN]

Another factor is...........it all depends on "where you live" because every city and state is different. If you live in a area that has alot of "hills/mountains/steep grades" its only natural your not gonna get that great of fuel economy.
Getting 18.6 mpg out of my H2 is NOT easy, and truthfully its kinda frustrating going 55mph, but considering payments are $1200 a month, and gas is $3 a gallon.....its worth going a little slower to gain the extra miles per gallon. You really have to drive it like you have a egg under your gas pedal, and truthfully if i lived in a downtown area/big city, then there is NO WAY I could drive this way. Truth is, if you drive slow in a big city, your gonna get run over. You have to dart out into traffic, and stuff....but where I live, I am on 2 lane country roads most of the time and running 43mph on those roads churning 1,100---1,200rpms it only logic your gonna get pretty good gas mileage.
As for the Escalade I had as a demo.......I was able to get 24mpg and again, thats driving like you have a egg under your gas pedal, and 100% pure interstate running 55---60mph with the cruise control on.

In the real world.......living in Atlanta.....Chicago.....New York...big cities, its NO WAY of getting those kind of numbers.
It really narrows down to where you live, and what the roads are like.
I am sure people in Mississippi get better mpg than people who live in East Tennessee. East Tennessee is full of mountains, and hills, where as Mississippii is very flat.