I have a 2001 suburban 325 4spd OD on 16" wheels, 3.42 and if I remember correct, it's 55 mph at 1,500 rpm. And, when driving my usual 70 to 75 get 20.7 mpg highway.
I am taking a ride upstate tomorrow with the family for a Christmas tree and will record the rpm at various mph. I will also measure the tire's diameter.
So if you are wanting good mpg I would go with a wheel tire combination that would give a 30 - 31 tire diameter. Jeffrey
