| Just a thought...
Since I've spent quite a lot of time working in France I know that our European neighbours don't measure fuel consumption in miles per gallon (obviously) or even kilometres per litre.
They measure it in litres per 100 kilometres.
Could it be that the imperial conversion is actually giving you gallons per 100 km? If that was the case you would be using 2 gallons every 62 miles = 31mpg
Even better if they were converting it at gallons per 100 miles in which case it would work out at 50mpg.
Either way those figures would at least be in the right ballpark | 
Jools
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