My wife and I own two 2016 X3 35i and change oil every 5K to 7K miles. I have not had to add any oil between oil changes for either of my X3. Oil consumption in my experience is less than 1/2 quart in 5000 miles.
Owners on other threads have reported a wide range of oil consumptions for the N55 engine. The link below covers a range from very little oil consumption to perhaps a liter every 2000 miles in the N55 engine. How the engine was broken in and is driven may affect oil consumption. Some owners report that the electronic device for measuring oil level is not always accurate. Overfilling the engine with motor oil may cause problems, such as when excess oil is whipped into a froth that offers poor lubrication. Some owners suggest not adding oil until the level is down about a quart.
https://f30.bimmerpost.com/forums/sh....php?t=1074877