Grand Scenic 3, 1.9dci FAP Poor MPG possible solution

Hi all,



I currently have a 2011 Grand Scenic 1.9DCI FAP and have been struggling with what I thought was poor MPG.



After a full tank to tank comparison and driving 488.7 miles I filled the car with 52L of Diesel and the car reports back a MPG of around 36-37 but actually works out to 42.7. After a brief conversation in the office this morning someone asked if it was possible the car was using US gallons ( I had never consider this before) after a brief calculation I work it out to be 36MPG using US gallons. I haven't had chance to look into this further yet but wondered if anyone else had found this?



And I suppose the other question is that if it is the case is there a way of changing it without a trip to the dealer?



Thanks in advance