The gasoline-powered Microjoule with a fuel economy of
10,517 mpg!!!
O.k., it was only going fifteen miles per hour, but even school children were acheiving 1,000+mpg.
More here:
http://www.shell.com/home/content/uk-en/society_environment/eco_marathon/results/shell_eco_marathon_2007_results.html
http://www.gizmag.com/go/7630/picture/35840/