I have a 2001 5.3 LS in my 49 Chevy pickup and I calculated it once and best I can remember it gets about 16-18 mpg. I'm runing a 350 Turbo with 273 gears all setting on 18" wheels.
"If you can't fix it with duct tape it's an electrical problem" 1949 5 Window 3100 Follow in the DITY Veteran of the USAF My Website