I don't think so, since we don't know if the bars can be correctly assumed to be representative of equal units of volume.
A cheap OBD2 display or dongle logging via Bluetooth to your phone can give you precise fuel consumption in liters.
My long-term method of calculating a fuel average is to log the odometer reading when completely filling a tank, then driving it until the reserve light comes on, then log the odometer reading again and use them for your calculations. Another way to improve accuracy is to fill it up when it hits reserve, log the odometer reading, and average the volume of the two fillups.
