To keep your car purring, you have to change the oil. Such maintenance produce eight billion gallons of used motor oil annually. Some waste oil does get re-refined to produce oil for lubrication or heating. And some just gets dumped. So it would be more environmentally friendly and provide fresh fuel if we could convert the old motor oil to something really valuable: new gasoline. And that's what a research team thinks they've done. They presented their work at the annual meeting of the American Chemical Society. Their approach involves pyrolysis, decomposing organic material with heat in the absence of oxygen. Pyrolysis can break down waste oil into gases, liquids, a little bit of solids. The gases and liquids can be converted into gas or diesel. But conventional pyrolysis methods don't do a great job with motor oil. The new technique mixes the oil with a material really good at absorbing microwave radiation. Tests showed that heating this mixture with microwaves was about 90 percent efficient at creating precursors to fuel—which beats tossing the oil down the drain.