+1 for more precise fuel start level in setup screen (displayed in litres and percentages). It's not difficult to do in real life if you're starting with a completely empty tank.
Also, my real car seems to know exactly how much fuel it's using (live MPG readout and "miles left in tank" display), and of course the tank capacity is no mystery, so I don't really see why you shouldn't be able to see how much fuel you have in the tank, digitally, more precisely than 1 litre increments.