Here's one you might want to look up in Snopes or Urban Legend: Ford's claim that it has a hybrid vehicle where a key element in the hybrid section is not a massive battery but—can this be possible?—hydraulic fluid. Actually, this one is true: Working with the EPA, Ford has developed a hybrid powerplant that uses hydraulic fluid to capture the energy from deceleration. Really. And it appears to make a lot of sense for delivery vehicles, school buses, garbage trucks, and other big, heavy vehicles that make lots of stops and starts. You might even see one in a 2008 Ford pickup.

Here's how a hydraulic hybrid works: When the vehicle needs to slow and the driver gets off the throttle or presses the brake pedal, rather than use the brakes, the motion of the drive wheels turns the gears on a pump that forces hydraulic fluid from a reservoir to a high-pressure accumulator containing nitrogen. Compressing the nitrogen stores energy that is released when the vehicle starts up; the pressurized nitrogen is allowed to expand again while turning the pump/motor that turns the drive wheels. It's not the hydraulic fluid that compresses—that would be the stuff of urban legend—but the inert gas being pushed by the nitrogen. With hybrid assist, the main engine can be made smaller, lighter, and more fuel-efficient.

HLA provides extra boost at startup with less added weight than some huskier hydraulic hybrid configurations. Hybrid hydraulic technology can be retrofitted to existing vehicles or incorporated into new vehicles; in the second instance, the system can be integrated into an existing drivetrain. A hydraulic energy storage system, backers say, can recapture about three quarters of the kinetic energy that otherwise would be lost as heat from the brakes. Compared to a battery hybrid, a hydraulic hybrid system can store and release large amounts of energy in a hurry. UPS and partner Eaton Corp.-Fluid Power have built a prototype delivery van; the UPS hydraulic hybrid can deliver about 100 hp for 20 seconds, or 1,000 hp for 2 seconds if UPS trucks actually ran in (not just sponsored) NASCAR.

Ford has been working on this for several years and has shown prototypes, including a functional Ford Expedition SUV and Ford F-150 pickup truck conversion. Some reports say Ford will use hydraulic launch assist on the 2008 F-150.