My last fillup was for 9.539G and I had 501 miles on that tank (I had reset the Trip B display after my prior fill-up). This calculates to 52.52 MPG. Yet the trip B display had said I was getting between 55.5 MPG. This has happened every time I've calculated my mileage, I'm not getting quite the MPG that the dashboard display says I am getting. It overstates my mileage by 3-4 MPG. I am happy with my Prius overall, but it puzzles me why the trip display mileage does not seem to be accurate.