Gas Indicator Distance

Considering the year and body style of your car, which you don't state, the reserve mileage may vary.
I seriously doubt that any two gas gauges are exactly the same.

So, the next time you're on a long run, take a can of gas with you and note the speedometer reading when the low fuel light comes on and then run the car till it runs out of gas and stops running. (then put in the gas from your gas can) Note the reading again and the difference will be how far your car will run after the Low Fuel light comes on. The terrain you're driving on and the amount of traffic you're driving in will have a great impact on that too.

When I leave my house and the Low Fuel light comes on, I have no problem driving all the way to town (20 miles) to fill up, at a discount station.
But I do try to drive for economy, more than I do with a full tank.

Cheers Mate!