Tom Magliozzi has a problem. The wacky co-host of NPR’s “Car Talk” needs to replace his beloved 1952 MG roadster. But in today’s car market, where should he turn? Is new technology about to transform the way we drive? Tom and his brother Ray hit the road for a light-hearted but shrewd take on America’s four-wheeled future in NOVA Car of the Future.

John Lithgow narrates as Tom and Ray mix their trademark slapstick with serious nuts-and-bolts analysis of what it will take to make our autos more energy-efficient. With a quarter of all the oil ever consumed guzzled during the last decade and oil supplies being drawn down faster every day, the brothers’ screwball automotive odyssey doubles as a serious environmental wake-up call.

Tom and Ray explore everything from the glitzy, high-octane North American International Auto Show in Detroit to the earnest do-it-yourselfers of the AltWheels Festival in Boston, where the brothers squeeze, clown-car style, into a tiny three-wheeler that, even at 100 miles per gallon, isn’t quite ready for the rush-hour commute: It can’t go in reverse. In Iceland, the brothers wisecrack with the driver of one of Reykjavik’s hydrogen-powered buses and find out how that country is positioning itself as a test-bed for innovative energy technology.

A distinguished group of engineers doubles as Tom and Ray’s straight men, including Lee Lynd of Mascoma Corporation, who is working to bio-engineer microbes that can produce ethanol from plant wastes, and Amory Lovins of the Rocky Mountain Institute, who is developing an ultra-light, full-size “green” car that is efficient and almost indestructible.

Also appearing are Andy Frank of the University of California at Davis, whose lab has developed a plug-in hybrid vehicle that “fills up” from an ordinary electrical outlet, and Martin Eberhard, founder of Tesla Motors, who wants to prove that battery-powered cars can be fast, stylish and travel 250 miles on one charge.

And then there are the giant automakers, with their penchant for producing 500-horsepower, gas-guzzling road machines that even a couple of car nuts like Tom and Ray find excessive — as the brothers emphatically point out to a cornered Detroit executive. A decade ago, Toyota paved the way to more efficient vehicles with its Prius. But will our current romance with hybrids lead to a breakup between Americans and their big, high-powered automobiles?

Which new technology will take off as the standard for the car of the future? With Tom and Ray, viewers learn that hydrogen fuel cells are the touchstone of zero emissions, since all the waste they produce is water vapor. But they require a new infrastructure for tanking up with hydrogen gas, which, as Tom and Ray note with a nod to the notorious Hindenburg zeppelin accident, is highly flammable.

Care to tank up on niblets? An ethanol-gasoline blend is already available at many filling stations, but doubts persist about whether ethanol represents much of an energy savings. Energy-dense lithium-ion batteries, like the ones that power computer laptops, could one day replace the gas tank altogether — but, as Ray points out, a pesky few of those batteries have spontaneously burst into flame.

Tom and Ray turn an expert, comic eye on the promise and pitfalls of tomorrow’s auto technology, and their quest inspires cautious optimism that novel green vehicles are about to become roadworthy. But do any of these future cars tempt Tom to give up his ’52 MG? NOVA Car of the Future reveals how the car guys answer this puzzler.