Ford Focus

Fuel-saving feature: Low-rolling-resistance tires
Savings: Around 1 mpg

Tires change shape as they roll, eating up some of the energy generated by the engine and giving it off as heat. Low-rolling-resistance tires fight that process with additional silica in the tread. Gene Peterson, tire program leader for Consumer Reports, said inflation pressure, tire weight, tread life, and the road surface also affect rolling resistance. But in optimal conditions, he said low-rolling-resistance tires could improve mileage by 1 or 2 mpg. The tire industry is lobbying for uniform standards, and for government-approved labels for low-rolling-resistance tires, like EPA mileage estimates. The 2009 Focus, on sale now, has low-rolling-resistance tires.