I have only had my Prius since early May, so I am still learning, but I have tried to minimize the tank variability by letting the pump shut itself off, then pulling the nozzel out to the end of the blatter and slowly adding fuel until it is totally full. It seems to be pretty consistent so far doing that, Just got 644 miles on my last tank, 10.5 gal, 61MPG. Hope you just keep getting better tanks every time! Congrats