BB, the gas six-cyl X5 is rated 13.6/9.3; the diesel's numbers are 10.7/7.5.
That's not all that great for a diesel. Our E300t sedan was in the low 8's in the city and low 6's on the highway and I took
liberal advantage of the roll-on torque. No "hypermiling" techniques driving that car!
Our car was as quick as the gas E320, got
significantly better fuel economy (most E320 sedan owners I knew could barely break 12L/100km city and 9L/100km highway) and COST LESS. You read right. Back in 1998 the E300 turbo was $59,900 and the E320 was $66,900.
As for size, we found the E-Class (and our 5-series) to be HUGE cars. Since selling them, we've stayed with smaller compact sedans and wagons (the C-Class, Forester and Corolla are about the same dimensions) and have never really wanted for more space.
On the occasions when we'd take the MB's to the dealer (warranty service) we'd have an ML loaner 99% of the time, and I hated it. Outward visibility was great for looking over the Miata in front of you, but for tight maneuvering in our neighbourhood, the thing was awful. A whole kid and her bike could hide easily in the blind spots. Also, the height of the backseat was a major pain in the arse when we had a little one in the car seat, as you had to heave it up into the seat, instead of loading it down into it. It weighed as much as an S-Class and had 2/3 of the interior space.
I would have kept the E300 for a million kms if it hadn't turned out to be such an unreliable POS. We ended up driving that stupid ML loaner more than our own sedan. Mercedes spent so much money on warranty work on that car I was truly frightened to drive it out of warranty.
