Originally Posted by ans2k
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.
I agree the speedo is off ay freeway speeds by about 2 MPH faster than you are actually going. I passed 2 radar signs and it's always the same. Driving 70 MPH the sign reads 68 MPH. I think the MPG is close too. I have calculated the mileage several times after filling up and it's very close. But I don't get anywhere near 36 MPG even going down hill.
The advertised MPG must be for a car averaging 45 MPH and wind aided with a 20 MPH wind at it's back.