I actually did this in the little Pulsar last week, and managed to get 10 point something per hundred k's 10.6 maybe. I got just over 400 k's to the tank. It's an auto, so not all that economical. (Manual, same car can get 600-700km per tank)

The reason autos are less economical than manuals is the fact that they (usually) rev harder between gear changes, thus using a bit more fuel. And often, they have one less gear than the manual equivalent of the same vehicle. Ie, the Pulsar I drive is a three speed auto, where as the same model manual is a five speed box. Travelling at 100km/h, it does make a big difference.

Helle, I was going to say that about sucking up all the garbage when running a car till it's almost empty. The sludge and cr*p that accumulates in fuel tanks is unbelievable. It really is sludge and bad for engines (says me who still does it )