Swedish web site lists these numbers for combined:

4.2 FSI: 13.6 liters/100km = 17.3 US mpg
3.0 TDI: 10.5 liters/100km = 22.5 US mpg

Sorry, could not find extra urban or urban.

17+ would be great but, the 18.8 gallon gas tank isn't very desireable compared to the 26.6 gallon tank in the Touareg!

Not sure where you get the 18 g's from.

The brochure for q7 is stating 100 litres which is spookily the same amount of litres as the us v6 and v8 models. Checked at dealer and they are saying the same.

This is a great change to the old xc90 we ran - it was just under 70 litres and useless for a long distance jaunts.

100 litres adds up to the gallons you mention too - in us gallons that is.