Fuel gauge not working properly

The digital reading in the cluster? If this is what you are referring too, this is simply a calculation and is generally accurate. However, I would not take it down to the mile because it could leave you stranded. Most of these gauges will not display a mileage once it is under a certain limit. Most are around 20-30 miles to empty.

Again, this is just a calculation based on the current driving conditions. So for example if you are at 20 miles to empty and then start accelerating aggressively you will not make it 20 miles. If you drive very lighted footed you may make it more then 20 miles.

Let me know if this answers your questions. Thanks