I have an 04 ext cab silverado with the small v8. on the road, I will range from 22 mpg to 24.5 mpg depending on the speed I'm driving and the road I'm on. The 24.5 is at about 65 mph on the interstate and the 22 is at about 75 on the interstate. I had a 99 grand marquis with a v8 and I got 27 on the road at 75 mph