Just an FYI...if you track the actual MPG & the OBC's MPG over a long period of time...you may find that they really aren't that far off even though they never may be the same at each fill up.


You can see this in the spreadsheet below. It shows the OBC & actual MPG calculation for every fill up in 2013 on my e53 X5. By the end of the year, the totals for each column was very close...there was only a difference of 0.37. After I saw this I stopped worrying about the difference because it was so slim.

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