Just thought I would point this website out to all of you. There is a feature that allows you to keep track of your actual mpg and then share it with the world. I just entered mine there (unfortunately, there was no place for a 1992 525it so I used the 1993 525it spot). If more of us do this it would provide useful information for all car enthusiasts.
http://www.fueleconomy.gov/feg/sbs.htm