These guys have conducted a scientific experiment, and the result left them floored. Their total distance of 111.9 km comes out to be roughly 69 miles (nice), which is genuinely pretty impressive!

Of course, this will likely vary from car to car, but it is fairly standard practice by most manufacturers to flash the 'Empty' signal well before the car is ACTUALLY empty so that you're less likely to actually sputter out by the side of the road.