The turbos, smaller engine blocks and advanced fuel-management systems available on the Cruze and others may not be as sexy as lithium-ion batteries.

WSJ: Is Chevy's Cruze Dulling the Spark of its Volt?

Vehicles with fuel-saving six-speed transmissions or cylinder deactivation systems let a big V8 engine run on just four cylinders on the highway.

FORBES: Joann Muller On The Automotive Industry