7k miles on my 2011 X5d, last tank got 22.9mpg (hand calculation) mostly slow highway traffic.

07 4.8i
mix city/highway: 15 mpg
highway: can do 18 - 19 mpg
aggressive driving: 8 mpg

08 3.0si and I find the trip computer to be pretty accurate after using fuelly.com with my receipts to compare. Getting about 15.5mpg with about 85% city driving - crap ton of stop signs and lights and usually carrying an extra 100lbs+ in the back.

wow for 3.0 i would think it would be in the 20's!
damn, i guess it all the weight of X to carry around

Not so good.

Same 3.0si engine in an X3, 2007 model. All figures with the same driver. Usually 91 AKI, but occasionally 94 AKI just to avoid the ethanol:

Around town, mixed driving: 10 l/100 km, equals 28.4 mpg Imperial, 23.6 mpg US
Worst tank ever, city only: 12 l/100 km, equals 23.6 mpg Imperial, 19.7 mpg US
Best multiple tanks ever, highway, 8 l/100 km, equals 36 mpg Imperial, 30 mpg US
Last highway trip, fully loaded, 120 km cruise: 9.5 l/100 km, equals 30 mpg Imperial, 25 mpg US
Towing 1500 lbs (same weight then as the E70), highway: 11 l/100 km, equals 25.8 mpg Imperial, 21.5 mpg US

My observation is that mileage depends a lot on driving conditions and habits. The worst tanks in the city, above, were 50% worse than the best tanks on the highway.

I am also on the heavier staggered 20 reps. Believe me, it's A LOT of stop and go everyday. I could only imagine what it would be if I had a 4.8 (so I can get to the next stop sign faster). I only get 21mpg when on highway exclusively and that's not even once a week.

Diesel would've been perfect for me. I had waited and waited and waited for the 3.0sd to come but I would've had to wait an extra 2.5 years beyond what I had already. Anyway, I don't do enough miles to really feel the pain at the pump. I love driving the thing when I do get the chance, that's it to me.

Mine is 14.9 MPG on a 2008 3.0si... I'm at 90% city driving in FL. Traffic lights here turn red in 5 seconds. Might I add in the tremendous amount of traffic ANY TIME of the day. FL has the worst traffic ever and I thought NYC had bad traffic... I miss NYC now.

I'm at 22.8 mpg in my 35d for the life of the vehicle 0-9500 miles doing the math by hand. I don't baby it, 80 on the highways and probably 60% highway/40% city.

I got 19.1 MPG on 2008 3.0si. Around 70% city / 30% HWY.

2011 50 5k miles wife 13.5. Me 15.9 to back that up I get 20mpg vs wifes 18 mpg I'm my 550. She is always on the gas.