If hydrogen fails as a transportation fuel, nobody can blame BMW, which has built prototype hydrogen-gasoline ­internal-­combustion engines for years and is now touting a version (at left) that’s undergone rigorous product development. BMW plans to give 100 luxury hydrogen cars next year to politicians, celebrities, and other people who can promote hydrogen. The engine can generate 260 horsepower, something a full-size electric car powered by a hydrogen fuel cell cannot now do, says Thomas Korn, senior project engineer for BMW’s hydrogen program in Oxnard, CA. Although hydrogen combustion leads to the formation of nitrogen oxides, BMW’s new car has sophisticated control systems that minimize those pollutants by optimizing hydrogen concentrations and engine timing. But will it ever make it to the mass market? It’s a long shot, says John Heywood, director of the Sloan Automotive Laboratory at MIT. Despite the need for cleaner cars, he says, “a feeling is growing that, really, hydrogen isn’t a particularly convenient way of doing all of this.”