Since you have bothered asked and since I have been fortunate enough to be using one for the last 2 months or so,
An Impreza GD2, 2007 (9 version), manual does,
8 - 8.3 km/l on weekdays under extreme traffic conditions
8.5 km/l on weekdays during school holidays
9.0 km/l on weekend travelling
above 11.0 km/l outstation
Note: above figures are facts and not fiction. Besides, I wouldn't want to be boasting of a Subaru with unrealistic fuel consumption figures when there is much more of it to talk about!
Like most have pointed out, driving a Subaru is not about saving money on fuel but more to do with the shear pleasure of driving it. Handling is simply out of this world compared to other Japanese models (I was using an EK3, Ferio Mi earlier)
cheers.