We have seen the future and it’s the Scuderi Air Hybrid Engine. Cars equipped with this innovative split-cycle engine will be able to get “twice the gas mileage of your current vehicle, and belch out only a fraction of the pollution.” Video after the jump.
The Scuderi engine could even boost mileage by recapturing energy normally lost during braking, as do hybrid cars. “Unlike current electric hybrids which store the energy in a battery, we are able to store energy in the form of compressed air,” says Sal Scuderi. That can be done by simply adding a small air-storage tank, which costs far less than the generators and banks of batteries gas-electric hybrids need.
There's a 4 1/2 minute video which explains in more detail how the Scuderi works.