Chevrolet Impala to Add CNG-Gasoline Option

General Motors Co. says its 2015 Impala debuting next summer will be the American market's only manufacturer-produced fullsize sedan to offer a gasoline/compressed natural gas bi-fuel system.

CEO Dan Akerson hopes to sell 750-1,000 bi-fuel Impalas next year.

A large trunk-mounted CNG tank holds the equivalent of eight gallons of gasoline enough to power the Impala's 3.6-liter V-6 engine for about 150 miles. The car's standard gasoline fuel tank gives the car an additional 350 miles of range.

The engine is equipped with hardened intake and exhaust valves and valve seats to handle CNG combustion. A GM supplier installs the CNG fuel system.

The specially equipped Impala includes a dash-mounted button that enables the driver to choose which fuel to use. When the CNG tank is depleted, the system automatically shifts to gasoline.

CNG costs about 40% less per mile of operation than gasoline. It offers a higher octane rating but delivers about 85% as much power. GM didn't announce a price for its bi-fuel package, but it estimates the system will pay for itself after roughly 60,000 miles of use.

The California Air Resources Board says CNG reduces a vehicle's greenhouse gas emissions 20% compared with gasoline.