That's why I use the same pump at the same station .... that and it's just convenient to me .... and a habit .... after all these years I know how to accurately compute MPG. I like how the Mustang doesn't reset itself when shut off but maintains it's readings until the driver resets it at next fill .... miles, gallons used, MPG, all reset.
Interestingly, while the odometer appears to be very very close, the speedometer reads almost 2 mph fast at 60. Guess that's maybe designed in to help keep the license clear for a more "pleasant driving experience"? I like fun driving, the knowledge that it'll go when I want to go, the sounds, good handling .... but I like saving some $$$ too (and I intend that October 1977 ticket, the latest of 9 which I received, to be my last ticket ever). Stretching those gallons over as many miles as I can is a game I play also. MPG is affected greatly by driver's habits. A soft gas pedal application combined with anticipation of hills, stops, and a large dose of patience will go along ways in saving $ at the pump.