My 78 CJ7, 258, 3 spd std, 4-something gears, 29 inch tires, used to get around 12-15 MPG depending on what kind of driving I did. My 05 TJ (4.0, 6 spd std, 3.07 gears, 31 inch tires) gets 15-20 MPG. I guess all that fancy computer control equipment adds a little bit of mileage. Both Jeeps...