It fits into a wheel hub and can double a car's fuel economy. That's the claim of Dr. Charles Perry, who says his plug-in hybrid retrofit kit can save America 120 million gallons of fuel per day. Big talk. But then, inventors betting on revolutionary uphevals need to talk as big as they think. The former IBM electrical engineer designed the kit to transform existing automobiles into hybrids by placing an electric motor inside each wheel. Perry recently took first prize for his invention at a green energy competition at the Tennessee Technology Development Corp.

At ten feet long, the Cygnet is two feet shorter than the Mini Cooper, and decked out in Aston Martin luxury. Based on the Toyota iQ, but with a few extra features including an upgraded interior and external detailing meant to match the luxury design of Aston Martin's significantly more expensive roadsters, the Cygnet -- which is currently a limited concept car that might debut next year -- seats three comfortably, or a fourth passenger can squeeze in behind the driver for a somewhat tighter ride.

The external-combustion engine predates its internal-combustion counterpart by nearly a century. Internal combustion won out for modern automobiles by way of its more robust production of horsepower and torque. But Segway inventor Dean Kamen is working up several new uses for the venerable Stirling external-combustion engine. The latest is a electric generator that can use almost anything that burns as fuel. It's the centerpiece of a new hybrid-electric scooter that may never need recharging.

This shiny little black car is the first real Chevy Volt—the first of many hand-built but bona-fide production-intent prototypes that will roll out of GM’s pre-production workshop in the coming weeks. This car is the next big step in the production process after the testing of the Volt “mules”—test cars with a Chevy Cruze body and a Volt powertrain. (We drove one of the mules last month; see our full review here.)

An oil company helping launch an electric car? The jokes write themselves. (Launch it where, into space?) But it's true: low-speed electric carmaker Electrovaya launched its Maya-300 car this week with help from ExxonMobil. The oil giant's "SuperPolymer" separator film is used in production of Electrovaya's lithium-ion battery. But wait, there's more.

The Riversimple Urban Car was nine years in the making. But when the diminutive, hydrogen-powered prototype debuted in London recently, the biggest difference between it and other fuel-cell vehicles wasn't its in-wheel electric motors or banks of ultracapacitors. It was its development-and-business model.

This week, a boutique builder of million-dollar supercars snapped up an established automaker with nearly 5,000 times its yearly output of vehicles. What's the deal? Is it a matter of super-hubris or another sign of a coming paradigm shift in the auto industry?

Call it the Dees-Milodon Engineering-Davis B Streamliner. That's the name of the vintage speedster in which automotive celeb Jesse James this week set the land speed record for a hydrogen-powered car. The daredevil star of Spike TV's "Jesse James is a Dead Man," reportedly hit just shy of 200 miles per hour in the modified, 40-year-old streamliner, breaking a previous record set by BMW.