Is it possible the access your mileage down to that amount of deviation? I mean if you could even tell you were off by 1 mpg would it be possible that there was another reason (besides the fuel type) that cost you 1 mpg? I don’t feel that this car or customer is capable of determining their mileage with such accuracy, I am sure many feel they can though.
If a customer came in and complained of his mileage being off by 1 mpg I would be looking for the “tin foil hat” to send him home with (he could keep the hat).My first question would be “how could you possibly measure this small amount of change”?