well, i once drove my old manual 1.3L 16V Charade for 180km around the sydney metro area after the fuel guage touched the 'E' mark. it sputtered as i was driving towards a servo, i pulled in, and it stopped just as i pulled up next to a bowser, and wouldn't start again until i got fuel
don't know exactly what economy that meant for the full tank, but it was in the 7L/100km zone