Experimental hybrid cars get up to 250 mpg

It looks like a typical Toyota Prius hybrid, but in the trunk sits an 80-miles-per-gallon secret — a stack of 18 brick-sized batteries that boosts the car’s high mileage with an extra electrical charge so it can burn even less fuel.

He’s part of a small but growing movement. “Plug-in” hybrids aren’t yet cost-efficient, but some of the dozen known experimental models have gotten up to 250 mpg.