Great question. If you are concerned AT ALL about fuel economy, then this is a no-brainer. Seriously, the 4.8 is TERRIBLE on gas, the worst vehicle I've ever owned in that respect. But it sure is fun to drive (and maybe that's why my mileage is so terrible). I didn't buy it thinking it was a gas guzzler, but I wasn't expecting it to be as bad as it is. Oh well.

I wanted the M Sport package, so I didn't really have a choice. If BMW USA offered the 35d with the M Sport, I think I'd probably go that direction.

I don't think you can go wrong either way. If you're considering a diesel, test drive the Q7 TDi too.