Sonata MPG indicator

I'm new to this forum and I hope someone can give me an explanation of hour the MPG indicator on my 08 Sonata calculates the mileage reading. What is the MPG reading really telling me at any given instant? What data is used to make the calculation and when is the data reset? I can get widely different readings under identical conditions such as on the freeway. Can anyone educate me? Thanks !

I'm new to this forum and I hope someone can give me an explanation of hour the MPG indicator on my 08 Sonata calculates the mileage reading. What is the MPG reading really telling me at any given instant? What data is used to make the calculation and when is the data reset? I can get widely different readings under identical conditions such as on the freeway. Can anyone educate me? Thanks !
I imagine it gets it's calculation depending on how much fuel has been used and the mileage. Whether it reads the fuel used on the amount left in the tank, or how much the computer predicts has been used, I don't know. You will want to reset it each time you refill, if you are wanting to know the mileage on that tank though, and it'll predict the fuel mileage on that tank so far.