I just got mine last week. You need to change it to 1.0 litre. It's not 3 litre. once you do this, you will get more accurate MPG readings. Mine was off the map. On a highway cruise, I would get 34, 38, 45, 32, 48, 55, and even a few near 100 mpg as I was coasting.
I find that the optimum MPG occurs between 60-65mph.