Recent mpg calculation

I wish to share my experience with my 2010 Honda Insight. It was purchased in May 2009. Currently the odometer shows 19503 miles. The last time I filled up with gas I recorded 48.9/mpg though the odometer registered 51.4/mpg. After many tank fillings I typically find the odometer reading to be 2-3/mpg higher. I don't know which is more accurate. So averaging the two numbers I got 50.1/mpg.