I got my Prius almost a year ago and have saved all gas recepts to estimate mpg over the year. I got my Prius right befor the first snow storm...we had a hard Minnesota winter. I just estimated my mpg and it came out to 48.8 mpg. would like to hear others mpg's.
Similar story here. I've had my C (2) for a little over a year. It's been a real gas to save so much fuel. If you are already tracking mileage you may want to consider using the "Fuelly" web site to help with your tracking. I've been fortunate to have the luxury of time to allow more back-road driving than in years past. As a result I've been able to coax my C's lifetime mileage up to 60 mpg, but I expect it to dip as we reenter winter.
12000 miles since July 28th, and I am at 54MPG. However this past month with cooler temps here in Las Vegas, I am close to 58MPG.
Will have it one year December 17. 21k, 54.5 mpg on fuelly. Higher summer, lower winter, and only two tanks below 50. DC suburbs, 27mile one way commute.
Over two and a half years my average mpg - whatever my fuelly thingy shows. That includes original wheels and tires for the first thirty k and then new wheels and tires for another 30 or so. I'm back to the original steel wheels shod with ecopia 422s. Over that period I've rarely had a tank lower than the high 40s, and had one tank (with a bunch of fuel left) of just over 500 miles and an mpg figured at the pump of over 114 ! Every fill up is recorded at Fuelly.