I have a 325ci and I do 70/30 hwy/city and get about 9L/100km.
When I do a lot of city driving I get about 10L/100km.
I also have a 5spd manual. Are you driving an auto?
If I drive economically, I can get 7L/100km on the hwy and 9.5L/100km in the city.
Are you using the correct oil? ie. 0w40 Mobile 1 or 0w30 Castrol?