The mpg on my car's dash differs from my own fuel consumption calculations - is this unusual?

I have a Jaguar XE, nearly two years old, which averages around 39mpg on the computer set for long periods. 2000 miles ago I decided to check real mpg by checking fill-ups against mileage and was surprised to find a figure of 35.5mpg. Is this unusual?

Asked on 5 October 2017 by JGH

Answered by Honest John
No, it's typical. Car mpg computers always show better than the truth.
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