Hmm I also live in Europe and this is a big consumption, bunt not for 3.0i.

For me, in Bucharest, Romania, the medium speed is from the bord computer ~ 22 Km/h and my fuel meter shows 13.5l/100 Km on 3.0d (diesel !!!)

On the highway the fuel economy is very good ! ~ 9.6l/100 km.

For comparison, my wife has a Subaru Outback 3.0 gasoline and in Bucharest it eats ~ 24l/100 km...

So you are good for the Europe city traffic.

Sorry that you cannot have a diesel made by BMW !!!