Darin is doing some amazing work to upgrade and test the aerodynamic improvements to his Pontiac Firefly, which was sold in the US as the Geo Metro. These cars were often sneered at for rolling off the assembly line with a tiny 3 cylinder engine. They didn’t sport much power, but they also went an incredibly long distance on a gallon of gas. Excellent data and documentation of the mods is available at MetroMPG, and on EcoModder.
MPG boosting tail cone