I am not familiar with the miles per gallon unit (we use lt/100km) but from some reviews I 've watched on YT it must be very good.
As for the Adblue, I was just wondering how close is the theoretical range of 12500 miles (20000km) to the real value. Either way, its not expensive from what I heard and I think it is a small price to pay for the (very strict) EURO6 standard...