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Yes, hdrygas, I also had a pretty big discrepancy on my first tankful and it has been going down over time. Furthermore, I seem to recall that the gas gauge moved off the fill line sooner on the first tankful than on subsequent tankfuls, so I suspect the dealer didn't fill it quite all the way.

After my first fillup (8 gallons), I computed 44.3 mpg while the screen read 50.7. However, after 4 fillups (~36 gallons), the discrepancy in lifetime MPG is down to 48.4 by calculation of total miles / total gallons vs. 50.3 by screen.

[Note that getting your lifetime calculation of MPG computed via the screen is a little subtle...Each time the screen MPG is reset (e.g, at fill-up), you must divide the miles traveled shown on the screen by the MPG shown on the screen to compute the gallons of gas used via the screen calculation. Then to get lifetime MPG average as computed by the screen, you add up all the gallons of gas used via screen calculation and then you need to divide the total odometer mileage by this sum. I created a little Excel spreadsheet to do this.]
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