In the video below, Motley Fool analysts Joel South and Taylor Muckerman take a question from a Fool.com reader, who asks: "Clean Energy Fuels Corporation (CLNE 2.15%), is it a buy? I've got a few shares of Westport Innovations (WPRT 2.09%) already and I feel we are in the transition phase of alternate energy and I feel that natural gas will eventually take off, that means I should act now rather than later? Yes or no? Thanks for your time."