Just another thought... with my manual transmissions I regularly "short shift" most of the time between gears versus running out the RPMs on acceleration in each gear. I normally try to shift at 2000 RPMs and try not to "lug" the engine below 1500 RPMs.
With auto trans the computers pretty much control the shift RPM based on engine load and throttle depression, of course. With autos you can punch the "power" button" for longer shifts and you can take fifth away away with another button, but for normal driving, I'm thinking the biggest MPG/MPL difference is driver style. I admit I don't drive as aggressively as I used to when I had somewhere to be and left myself little time to get there, or got stuck in some damned traffic jam on the interstate system somewhere. Now a days it's more of "no place to go and all day to get there".