Am driving a 2000 6-speed 3. 54 gears. Run 60 MPH, mostly interstate, 110 miles a day 5 days a week. Tires are at 70 psi, folded my mirrors in. Shift at 17-1800 RPM. My average mileage is 25. 6. Am considering a smarty. Trying to gain 30 MPG. Electric fans are in the plans also.
If you aren't running additional timing, a Smarty will get you maybe half way to your goal. 25 is the best I can get at steady freeway speed but that's with added timing.