PBS NOVA. John Lithgow narrates as Tom and Ray, brother co-hosts of NPR's Car Talk, 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 up in 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.