Reddit commenter nomopongo beat us to the punch, so we'll just quote him/her here: "The Prius does not use a conventional fuel tank, and because of this, you can't use the refueling numbers in order to calculate MPG, unless you do it over many fill ups. The Prius uses a resin gas bladder in order to minimize fume-related pollution. The article is wrong."

The Prius hybrid indeed uses a laminated resin fuel bladder inside its gas tank to reduce the amount of gasoline fumes that escape, thus reducing air pollution. Nominally, the gas tank of the Prius can contain 11 US gallons, but owners of the car have reported fill ups from "empty" varying from 8 gallons to over 12 gallons.