Banks 85-19 Ford F250/ F350 10.25in 12 Bolt Black Milled Differential Cover KitFuel Economy was tested on the Mustang dyno using the OBD II fuel flow rate and vehicle speed data, as well as the Banks emissions analyzer to measure fuel economy calculated from tailpipe emissions. The dyno was calibrated to simulate a 7,500 lb vehicle with an engine output of 30 HP required to maintain a 50 mph steady state speed. The truck was warmed to operating temperature then held at a constant 50 mph for a fixed length of time to procure an