My first trip - about 900 miles
I tried to run around 80 mph when possible and averaged 30 mpg with one passenger and a hatch full of luggage. I found the XF very comfortable and so did my wife ridding passenger. I used no noticeable amount of oil. The car ran perfect. The outside temperature hit 104 degrees while we passed through KY and the air-con kept us cool. I don't think you can ask much more out of a car.
One note, the XF will hydroplane but I'm used to that with the our Vette.