Difficulty in changing "Display Units"
 

I recently moved to Canada and imported my 2014 CUBE (not a simple, straightforward or inexpensive process).
My odometer displays MILES, but I now buy gasoline by the LITRE.
The "UK Display" seems perfect for me (litres, miles, UK MPG),.....however......
... when I add a fuel-up it wants the quantity of fuel In GALLONS.

Am I doing something wrong?

Go to edit vehicle. Set Track fuel in Litres.