We must compare "bricks" to "bricks"
A new heep gets around 14mpg stock, and with lift and tires and other that drops to ~12mpg or less.
My rig, with a 4.3, snorkle, 33's, and lift... gets as high as 19mpg, and I'm hoping for 20mpg with my cruise control done.
So I'm pretty happy with what I have.
Try slowing down, it makes a difference. Once I start going over 70mph, my mileage drops to ~14mpg.
Kary

1987 Mitsubishi Pajero "Modified"
The other original Mitsu brother
Northwest Trailmaster