When I drive on the Highway at 65mpg for a 100 mile round trip I am only getting around 27mpg at the pump. Computer usually says around 29. I guess I can live with that even though it is not that great. The problem is that my wife commutes in our small town with our car. She drives less than 3 miles round trip to work and back. She doesn't even let the car rev over 2500rpm. The computer says that she is only getting 15.6MPG with 100% in town driving. I realize that city driving is less, but this is as bad as my 4200lb, 4x4, V6, brick shaped Jeep Liberty. Is there something wrong with my car?