I guess it depends on how OFTEN the pumps are checked. My sense is that this happens once a year or even less often.Pumps are also regularly checked for accuracy by local weights and measures, so these tend to be pretty accurate.
This brings up an entirely other point to mpg - but a major consideration... Fuel can have different volumetric values based upon temperature and altitude and other geographic concerns. MPG may also vary based upon chemical formulations..
Since you know more about fuel pumps than I ever will, can you suggest why I'm seeing this up and down the East Coast since the weather turned cold:
After inserting the nozzle into the filler neck, you squeeze the handle. The price and gallon dials on the pump start spinning, but there is no sound of gas going into the tank and you can't feel fluid moving in the hose. Somewhere between .75 and 1 gallon, you suddenly hear the sound of fuel starting to enter the tank and you can feel the hose jerk slightly as the fuel starts to go in. Everything is normal from that point on.
The lag between the dials starting and the fuel flowing varies slightly between pumps at the same station and between stations, but almost every pump has some. Again, this seems to be associated with how cold it is out.
No matter what - there is still no 100% accurate and foolproof way to get your actual MPG. It is all going to have at least one variable.
PS - as an IT geek and support guru, I feel more accuracy based upon the systems installed then anybody's manual calculations. The system's calculations are based far more on "I drove 325 miles and put 10 gallons in the tank."
My Foz only has mpg calculations based on each of the two trip meters, so there is no instant mpg display possible.I drive a 2010 Forester.... That being said, what sort of calculated mpg do you all get with similar habits?