One of the first things Eric Mattessich discovered in engineering school was that the typical internal combustion engine blows about 70 percent of the energy it creates straight out of the tailpipe in the form of heat. So, he wondered, could he adapt the kind of heat-recapturing mechanisms used to make powerplants more efficient to work on hybrid cars? “The technology has been around since the 1900s,” he points out. “It’s just that no one has put it into such a small package before.”

Earlier this month, we told you about an alternative oil for 2-stroke engines made from beef tallow. As you may remember, 2-stroke engines are tiny and powerful, but inefficient and heavy polluters. For years, engineers have tried to combine the efficiency of a 4-stroke engine with the power of a 2-stroke, only to come up short because the technology was simply not yet advanced enough. A team of UK researchers have finally solved that puzzle with a prototype they call the 2/4SIGHT.