Car Runs Mostly on Air

Developer Zero Pollution Motors is working on a compressed air vehicle (CAV) that could run "all day on nothing but air and a splash of salad oil, alcohol or possibly a pint of gasoline." Cost: $20,000. Timing: 2011.  When using regular gasoline, the flexible-fuel-format (and tiny) car would average 106 mpg, more than double the industry-leading Toyota Prius.

http://www.livescience.com/technology/081103-air-car.html