I get 38- 40 mpg on the highway (depending on my speed) with my 2010 AT Fit. Get around 29-30 mpg in town.

 

it's been tested and proven, the Fit auto, gets better mpg then the manual, the reason, lower rpms.

the manual is fun to drive though, I've had both, I prefer the automatic.
The 6spd manual would probably be better mpg then the 5spd manual and the 5spd Automatic, but it hasn't made it's way to North America yet.
only the Jazz has the 6spd, the asian and european versions

 

Nitpicks: its true, but in the domain of interstate speeds. Back country road speeds mights favor the MT. Also, its a combo of gear ratio greatly favoring the AT and a lockup torque converter (which greatly reduces the energy loss in the AT).