The mileage calculator to actual mileage will vary slightly by vehicle. Only was to know is to check both ways starting from a full tank, run most of the gas out and then refilling it to check actual.

the 49.9km/h is your average speed since you cleared it the last time. There is a also a range calculation but it would be kms only. Range will change based on current rate of consumption.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas