My MY09 Impreza, 4 cylinder, can barely hit 11L/100kms in pure urban driving ...but I went to Blue Mountains in January in it, mostly motorway driving(4 adult on board), the average fuel consumption was only 8.7L/100Kms,.
So, if you onlydrive in the city and want to save on fuel bill, get a compact car... like a Yaris/Mazda2/Swfit/Jazz/Polo/Fiesta or any of the offering from Korea