I used to get between 17 and ~22 with 3.08 gears. Thats at about 2200 rpm at 70-75...
Then, my 4th gear died, so now at 70-75, ill be running at about 2600-2800 rpms, and I didnt lose much mileage, interestingly...
This is with my '93 Sport with 289,113 miles on the clock.