09 35d here. The only #'s I have paid attention to are highway #'s. It is fairly easy to get 26+/- mpg highway. I tried to be gentle with the throttle and got about 28.3 MPG on a 35 mile highway tip last week. Cruise was set at about 75 mph most of the time. Both of these figures were from the computer.

21.9 lifetime average (17k miles) according to the trip computer (2011 35d). Never seems to sway from that number. Good mix of heavy footed acceleration around town, and highway driving at ~80mph.

Just did a round trip from Chicago to Denver and back in the past week. Almost all Interstate driving at 65-75 mph. MPG went between 27 and 31 mpg for the trip. Best mpg was from Denver to Iowa, probably due to the wind at my back and the drop in elevation.

I've noticed that there is a major drop in the diesel mpg when one increases the cruising speed from 60 to 70+ mph -- that last 10-15 mph seems to hit the mpg hard.

If it will be your sole automotive thrill, hard to not say F-it, and get the 50. Just budget ~2x for fuel costs.

But if YOU have faster cars to play with, then a diesel is a near perfect solution for an SUV that is a wife driven, family trip type car.

IMO

A

25.8 MPG
 

After 32,000+ miles and 95 fill-ups, the average mpg on our 2010 X5d is 25.8

The lifetime mpg on my 2011 X5 35d is 21.2 @ 36k miles. Same driving on my previous 2008 4.8 (which has similar mpg sticker to 5.0) was 14.1. You do the math!

Wow. Anyone want to buy my 50i? I am digging the 35d. All the fun and less pain at the pump.

My X5M 50d has just clocked over 5,000klm and with 70% City & 30% Country driving I am getting 9.3ltr/100klm, hoping it will get down to around 8.9ltr once it gets run-in.

The 50i rocks. Don't get me wrong.

38,000 miles and the lifetime average is around 20 MPG, between 85% and 90% "in town" driving. It's the wife's primary vehicle, and she doesn't have a commute really (a few days a week, 5 miles, all back roads.)