I had another GMC Extended Cab 4x4 before this one, and it was a little better on gas. It had a V-6 with a 5 speed manual transmission. I averaged around 18 MPG, and could get 20 on long highway trips.
Don't get me wrong, folks. It would be nice to spend less on gasoline. But I chose these trucks because of their utility, rather than their fuel economy. I have adequate and comfortable seating for five. I can get through all kinds of road conditions (and off-road conditions). And I have the ability to haul large, heavy items when I need to do so.
Mrs. O drives a Pontiac Bonneville, and it goes farther on a gallon of gas ... we got close to 30 MPG on our last Texas trip. I don't find the Pontiac's seats to be as comfortable as those in my truck. i think it has a lot to do with the inflatable lumbar supports in the truck's seats, and the additional leg room.