Lightning Hybrids debuted their LH4 100 MPG hydraulic hybrid at this week's Denver Auto Show. The LH4 uses a three-cylinder biodiesel engine mated to a hydraulic pump/motor for both long-range mileage and short-range get-up-and-go.

The light-weight LH4 hopes to win the $10 million Automotive X Prize, set to be awarded to a safe, production-capable 100 MPG vehicle. We can't vouch for the marketability or safety of this vehicle, but the idea is an interesting twist on the gas-electric hybrid, substituting a hydraulic pump/motor for the electric motor. The goal for this vehicle is to sell in the $39,000 to $59,000 range, sip gas at a rate over 100 MPG, and achieve a respectable 0-to-60 MPH time of around six seconds.

We don't expect the little three-cylinder diesel to have much trouble in the fuel economy department and, for short bursts of acceleration, a large hydraulic motor hooked up to a tank of compressed liquid seems like a powerful enough source. Why store electrons when you can just store molecules?

[Poupular Mechanics]