If the tank is truely empty (ie you've not just run the car until it stops) then I'd suggest adding some fuel and running the car until it dies. The meter reading at that point will then be your "practical" empty reading, as there is a surprising quantity of fuel in the tank that isn't able to be picked up, and I'm not sure whether the lowest reading of the sender is in that "dead" fuel area, or not. Wise words. Jonathan