Just crossed the 18,000 mile mark with my 2013 X3. My mileage is 27.5 hwy and 23 around town. I've tried different driving styles/modes with highway driving with my best mpg being just over 28. Average highway trip is 350 miles one way.
2015 BMW X3 xDrive28i Deep Sea Blue Metallic / Leather Oyster Nevada
2013 BMW X3 xDrive28i Vermillion Red Metallic/Leather Nevada Mojave, Retired with 49,750 miles