21.9 mpg avg on my daily commute, and that is with aggressive driving against these lousy daily commute drivers.

Around 25 MPG, 50% city-highway, with a light foot. Once the turbocharger kicks in it gobbles diesel fast.

One thing I've noticed is that the AC seems to cause a big drain on the 35d, more than I recall on previous gasoline-engined cars. When the weather is in the 40s to mid-60s, I can turn it completely off and open the sunroof and/or windows, and the MPG goes up by 2-3 MPG on my daily commute. The X5 also feels more responsive, although I can't say whether that is a real thing or just because I can hear more of the engine when the windows are down.

What's annoying is that the X5 (and many other BMWs and non-BMWs) insist on running the AC all of the time. I've heard the explanations/excuses that this dries out the air, blah blah blah, but I live in a very dry area, so that's idiotic. The X5 also doesn't appear to have a "vent-only" mode, and instead has to have the fan on to get any air moving. This air is apparently ducted through the engine bay or something, as it is always warmer than it should be. I love AC and the automatic climate control on the X5, but it shouldn't exclude being able to use it for vents.

One note on the trip computer, mine has never been accurate, and I check it against a manual calculation every time I fill it up. It's always lower than actual, and has been off by no less than .3 and as much as 1.5. What I wish we had was a digital readout of the instantaneous MPG, like I had on my e92 335i, instead of the 90's-era analog gauge.

I've consistently had 21 to 23 in town which is majority of my driving. My last 200 mile trip to the mountains and back was just over 28. I have about 16,000 miles on my 2011 now (May 2011 purchase). My diesel prices have varied from a low of $3.70 a gallon to $4.29 now (winter months higher...summer that better price).

I do also find the AC a big drag on performance and when temps dropped here and I no longer need AC (I just switch off the AC button after hitting Auto on the climate control) the X has nice throttle response and feels quicker.

I've not regretted the purchase. Always seems to have plenty of grunt to get the job done and put a smile on my face. As another poster said if you go to the 50i mileage is probably not your biggest concern. I think where the diesel shines is the balance between mileage and performance. My .02 cents.

I typically leave the fan on at 2 or 3 'bars' to circulate air, just like any other vehicle - no AC involved if the 'auto' and 'snowflake' buttons are not lit - and at start-up, it remains how it was left when turned off - it does not "insist on running AC all the time" (unless, perhaps, the key memory is set to have AC on). If the temperature setting is lower than the ambient temperature, no warm air should be coming through.

In truth, pretty crummy. My wife's 2011 X535d gets 14-15 mpg in all-city driving with lots of stops and gos and carpool waiting lines; a/c on most of the year. She's never been the most efficient driver, but still.

I get 21ish around town; 25 - 28 highway. Usually 25, as that is the 80 mph rate. I can't imagine how to get 15, unless I just park it for 6 hours with the engine running... Btw 2012 35d with about 6500 miles on it.

22-23 90% city wife driven here.

When we do 400mi all freeway trips the speed is really key. Driven at 80mph I can average around 24-25mpg.

One time I decided to drive exactly the speed limit - roughly 70mph and I averaged 29mpg door to door. This just goes to show you the aero effects of that last 10mph - it isn't linear :)

New member here. I just bought a 09 X5 35d with 38k on it. First tank I averaged 23 mpg, second tank I switched to Cenex diesel, and got 24.11 mpg. My driving has been 24 miles to work at 70mph. Then some around town driving as well. But since this vehicle is new to me, I have been really trying to get good mileage.

James May of Top Gear mentioned same about how much more horsepower is needed to push Veyron (that he drove top speed) the last 50mph of the range compared.

Sometimes folks here complain that their 35d doesn't reach the official 26mpg number, while driving at 80mph. Meanwhile they forget that 35d was most likely tested at 60mph, and 35d easily does more than 26 mph at that speed.