VW once built a supercharged Polo that returned over 100 mpg

Volkswagen’squest for efficiency began well before lawmakers started linking emissions to fines. It sold several fuel-sipping, Formel E-badged models during the 1980s, and its research and development department took fuel economy to the next level by building a prototype named Öko-Polo designed to use only three liters of diesel per 100 kilometers, which represents about 78.4 mpg.