If it’s any help SpinaB, we have the 2 litre petrol X1.
It gets mostly local use in town, often journeys of only 2 or 3 miles and does 37mpg in those circumstances. The extra refinement and smoothness of the petrol engine in stop go traffic is very noticeable.
On long runs it will do 50mpg if sticking more or less to speed limits and relaxed driving. The best I got was a 300 odd mile round trip where I was not in a hurry, didn’t exceed 60mph and got 56mpg.
Obviously not like diesel consumption but not such a big difference as was true of old tech engines. Factoring in fuel price differences, especially in winter when heating oil demand shoves diesel prices high, we are happy that we moved from our previous diesel and haven’t noticed the difference in fuel bills – but then we have only done 9000 miles in the year we have had the car.