the mileage reader is off. but so is a lot of other things. your odometer is off too and so is the time. your time is increasing faster than time itself and your car is traveling a lot less than what it is telling you. if you take out your gps(phone, or hand held) it will tell you that the impreza is off by about 2-5 percent, depending on the car. and the mileage read out is usually off buy 5-10%. if you factor in the correct mileage, then the MPG read out is not "that" far off. still incorrect.