X5 3.0i fuel consumption problem

[128auto]

Hi all, this is my first post, just want to say hi to everyone. I purchased a 2005 X5 3.0i 3 months ago, so far so good. The only problem I have is fuel economy. Yesterday I filled 57 litres of gas and the trip is reading 323km. 19L/100km, isn't that a bit too much? I have no idea what's going on, my wife is driving the X5 most of the time, she said she is easy on gas pedal, I would say 50/50 city highway driving. Looks like it sucks gas more than a 5.7 GMC pick up. Any idea? Thanks in advance