So far I have mainly used Comfort mode (DCC) which selects Normal (not Eco) for engine. Last fill up was 358.1 miles, trip said 40.0mpg but calculations revealed 39.1mpg, which continues to be surprisingly close to reality. So far I'm on 36.9mpg over 1200 miles, which I think is OK.
The only thing I noticed was that the gauge looked nearly 1/4, but the range was down to 65 miles - which seemed a much more accurate representation considering the amount of fuel I purchased, so I'm guessing the gauge drops quite quickly as it approaches empty.