the 3.0 benz in the 2007-2008 are getting 23-25 with stock configeration, I we had the 6 gear the benz would be close but we only have 5 gears, less mpg on highway.
Real MPG are not the same as lab treadmills.
Fiat's new diesel engine uses Multi Air technology. Airflow into the engine is managed electronically cylinder by cylinder, through the inlet valves, not the throttle. We will see if the claimed 34 mpg is acheivable in due course.
I think it will not have Multiair, but Multijet technology that is about injection system, not valvetrain. In this engine valves are moved by conventional finger followers.