If you want a reference my 96 Suzuki Alto, 660cc turbo, gets average 6.2L/100km and I am not light on the throttle and drive daily. Would probably get better if you drove it like a city car should be..
Tires are 155/65/13.
Look after it well of course but most of my journey to work would be on the motorway. 5 speed box though so it's not too bad in terms of revving it's nuts off.
Lots of fun, highly recommended.