Wow, I'm not getting this or maybe I converted this all wrong. Our 35i best combined mileage was 10.5L / 100 km or 22.4 miles / gallon. Our worst fuel consumption thus far was 11.2L / 100 km or 21 miles / gallon. Looking at our E70 that had the 4.8L I was averaging 17L / 100 KM or 13.8 miles / gallon.
I went on
www.fueleconomy.gov and they state the following which seems to be in line with my wife's X5:
City 18 MPG
Combined 21 MPG
Highway 27 MPG