My last long trip (LA to SF and back, via I-5 and the Grapevine) got me 35.1mpg on the way up, 35.7mpg on the way back. My DTE versus the odometer had me at about 610 miles per tank, had I kept going.
No doubt about it....the car's range is great. But until the human body evolves a bladder than can withstand several cups of coffee/water/soda and 6 hours in the car, both the 335i and 335d drivers will have to stop at some point!
Then again, I like stopping, 'cause then I get to floor it on the onramp and unleash those 425 lb/ft!
We can argue the economics of the i vs. the d all day long. It's gonna be a personal preference. Personally, I love the bass tone of the engine, the torque curve, the smoother throttle tip in, and much better mileage than the 335i. Oh, and my '08 335i had a tranny failure at 612 mi and the HPFP failure at 4000....the 335d has been flawless so far.