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. As auto sales dip, aiming for higher mpg is likely a smart business strategy. After all, it's what sells: "The Prius, the Yaris, the Matrix, and even our Scion brands. Anything that's going to give them the most miles for their buck," is what Missouri Toyota dealership sales manager Brian Cowles says of what's hot.

As far back as 2005, however, experimental vehicles were getting up to 250 mpg. Getting these sorts of vehicles into production requires serious industry and political willpower, not just hot air. Meantime, there are a slew of hybrid SUVs and trucks that get around 21 mpg ... progress?

[How Hybrids Work]

This article is from the LiveScience Water Cooler: What people are talking about in the world of science and beyond.