I ran my second tank down to 0 miles to empty and filled up about a mile after hitting 0. The gas gauge was just touching the bar next to the E and the orange low fuel gas pump light had been light for the past 30 miles.

The car took 14.4 gallons to fill up, and had 624 miles on the tank (topped it off with a second click) at the same pump I gassed up with the previous time. I calculated 43mpg for the tank. I had about 2.8 gallons left in the tank - plenty of reserve fuel!