It’s tough to make sense of Chrysler’s forays into hybrids and other advanced fuel-saving vehicles. You could imagine the company playing to the strengths of its Dodge-badged vehicles—pickup trucks and minivans come to mind—by offering high-mpg hybrid versions. After all, there’s pent-up demand for a hybrid minivan or pickup truck—segments that don’t yet have gas-electric options. But those hybrids remain ideas at this stage. The company dipped its toes into hybrid waters with the Dodge Durango and Chrysler Aspen Hybrids and has dangled notions of electric vehicles—but for now, it looks like its only realistic green (or semi-green) play is diesel. That’s where Jeep comes in. The Jeep Grand Cherokee has been one of America’s quintessential SUVs for more than a decade and a half. The diesel version offers 30 percent better fuel efficiency than its gasoline counterpart. But the combined city/highway EPA fuel economy rating hovers right around 20 mpg, and the vehicle doesn’t pass stringent air quality standards of California, Connecticut, Maine, Massachusetts, New York, Pennsylvania, Rhode Island, and Vermont.