On a related note, how about removing obviously incorrect data? I hate to single out a user, but here's an example. In the Prius II database, car name "silver prius" belonging to grant_MH has an average MPG of 0.1. If you look at that car's history, there was a data entry error. For one tank, 70,726 gallons of fuel were used. Another car/user entered one tank of 75.6 gallons for 393 miles. I have to wonder if these two bad data points are messing up the overall average for the Prius II database.