Here is the problem with your analysis though, F30 335i gets better fuel mileage than the E90, whether automatic or manual, similar weight. Thats another positive for the N55 (for manual) and N55 + 2 gears (automatic).

Agreed on "less rolling resistance due to no awd; less frontal area and lower drag coefficient so less total aero drag; 1200 or so pounds less to lug around"

Lets get the experiment going and lets see what data points we collect over the next month. I hope others join in and "no trolling allowed".

What parameters should we set so there is no cheating