My wife (who drives the Hemi "D" more than me), has informed me that her mileage around town has been an abissmal "9 mpg" as of late! Before I installed the 20" wheels and tires, and a Cat back exhaust, she was getting 11 mpg around town. She has been using the electronic roof console display to calculate. Now I know that switching the wheels and tires from original, would probably show a 2-3 mph discrepancy on the odometer, but is it possible that the new wheels and tires and the exhaust are fooling the trucks fuel mileage computer???