Excessive gas consumption. Please help

[Pruzina]

Hi guys. I have E53 3.0 180 mils. My gas milage is craaaazy high. I read lots of articles here and nothing helped me. My daily MPG is 13-14. Roundtrip Orange County - Las Vegas (more than 600 mies) 16.4 MPG (99% freeway cruise control 75mph).

If somebody wants to tell me that it is normal for car like this becouse its heavy suv. 4700lb
For comparison my previous car Mercedes benz E500 V8 4200lb. Daily gas milage 17. Vegas round trip over 23.
Okay MB its lighter and has better aerodynamics smaller wheels but its 5 liter V8.
So when I was buying X5 I was expecting fuel economy about the same.

Obviously there is something wrong with the car. I have to state that the car is running 22" wheels which is not the best for economy but that is not gonna be the problem.

condition of the car:
NO CHECK ENGINE
Oil changed
spark plugs changed
brakes completely changed (no drag at all)
alignment done
tire pressure OK
no gas leak

the only things I see could be problem are:
1) 4x4 light on (trying to localize problem and fix it. most likely steering sensor) appreciate advices

2) MAF sensor recently cleaned with no positive result (could be faulty and needs to be replaced but no check engine)

Any help appreciate. I'm desperate a read every article saw every video. I own the car about 3 months I Love the car like no car before but this is gonna kill me