I am on my 3rd VW Stationwagen now and I have done Southern Germany to Venice and back with 3 adults and 2 teens plus luggage like we were going to Turkey for 4 weeks. 8no we were on cruise for a week) All this on single tank of diesel and that was about 1.665 Km and some to spare.

This does how ever also depend on you own personal way of driving. Manuals are more efficient than automatics, shifting up faster plays arole, how you pull away at lights or stop streets, do you diving looking ahead and anticipating the traffic so that you don't have to use brakes excessively etc. It plays a role in how much fuel you will end up using. Then again those of us paying 10,- UDS and more for a gallon are probably more efficient now any way.