It gets 100 gajillion miles per gallon.

Scientists at our own Rice University have constructed a ‘[1] nanocar,’ barely the width of a DNA strand:

The nanocar consists of a chassis and axles made of well-defined organic groups with pivoting suspension and freely rotating axles. The wheels are buckyballs, spheres of pure carbon containing 60 atoms apiece. The entire car measures just 3-4 nanometers across, making it slightly wider than a strand of DNA. A human hair, by comparison, is about 80,000 nanometers in diameter.

The experiment hit a snag, however, when the car broke down on 59, and was towed by a microscopic Safe Clear wrecker.