OKLAHOMA CITY - Hertz is planning on testing 10 compressed natural gas vehicles at Oklahoma City's Will Rogers World Airport next month.

The company in a news release says using compressed natural gas reflects a growing interest in fuel-efficient rental cars.

"As more low-emission, fuel-efficient vehicles become available for general use, we will continue to expand our rental fleet," said Mark P. Frissora, Hertz CEO.

Hertz says it chose Oklahoma because the state has a number of fueling stations that sell compressed natural gas, or CNG.

Compressed natural gas costs about half the price of gasoline, and emits much less carbon dioxide and monoxide.

The move follows a shift to more fuel-efficient cars by Hertz and other rental companies.