[cleanspeed1]

There are a few things that could be going on here. How does the lady you chatted with drive? And the next question would be, between the 4 speed auto and the 6 speed auto, aside of the extra 2 gears, was the final drive ratio affected? Where does she live ( terrain and temperature )? Fuel quality? Was there an engine / drivetrain calibration difference between your vehicle and hers? ( No doubt there was )

The driving style, you know, has the greatest impact on mpg.

Also, all the extra hardware spinning inside the 6 speed auto might impose a slight penalty in losses; but unless both cars are tested back to back with the same driver, same driving style, it's pure speculation.