The price of filling up your car's gas tank is not the major concern as it was when oil was trading near $150/barrel. Oil is currently trading in the low $70s per barrel, about half of its 2008 all-time high. Due to the dramatic sell-off from the highs, the urgency for green cars has been sidelined by a large majority of consumers. But the major automakers are still making a push for electric and natural gas-powered vehicles.
The future of electric vehicles produced by everyone from Tesla Motors (Nasdaq: TSLA) to General Motors has been grabbing the headlines. At the same time, the idea of vehicles running on natural gas has yet to gain steam. The attempt to gain traction was once again thwarted in early August when a bill to give incentives to fleets of natural gas-powered vehicles stalled in Washington. (Learn more about the financial impact of green vehicles; see Hybrids: Financial Friends Or Foes?)

IN PICTURES: Top 10 Green Industries

Natural Gas Vehicle Plays

Big names and big money are not giving up on the idea of expanding natural gas vehicles, and one of the biggest backers is billionaire T. Boone Pickens. Pickens is the majority shareholder of Clean Energy Fuels (Nasdaq: CLNE), a play on the natural gas vehicle sector. The company covers the entire process of running natural gas-powered vehicles. CLNE provides natural gas conversion systems and fuel systems that equip vehicles so they are able to operate on natural gas as their fuel source. The company also finances, builds, owns and operates natural gas fueling stations throughout the country. Technically the stock has been struggling to move higher, but it is holding support at the $14 area. Fundamentally, the company lost 58 cents per share over the last 12 months and trades at an inflated price-to-sales ratio of 5.8. Too rich for me.

Canada-based Westport Innovations (Nasdaq: WPRT) develops and markets engines and fuel injection systems that run on fuels such as natural gas, hydrogen and liquefied petroleum gas. Fundamentally, WPRT is about as attractive as CLNE; however, technically the stock has held up well and is sitting just above major support at the $16 area.

Fuel Systems Solutions (Nasdaq: FSYS) manufactures systems and components used by the transportation industry to build vehicles able to run on natural gas and other alternative gaseous fuels. The company's components control the pressure and flow of the gaseous fuels so they can be used in combustion engines. FSYS differentiates itself because it makes money and trades at an attractive P/E ratio of 9. Technically the stock is in a neutral phase, and the next few weeks will set up the next move for the stock.

A Boom For Natural Gas

If you believe the fleets of natural gas vehicles will grow in the coming years, it will likely increase the demand for natural gas and boost the bottom line of natural gas companies. The First Trust Natural Gas Index ETF (NYSE: FCG) invests in a basket of natural gas companies in the U.S. and would be a great play for investors looking to gain exposure to the entire sector.

Trend Or Fad?

The push for widespread natural gas vehicles may be a dream of T. Boone Pickens, or it may turn into a hot fad or possibly a long-term trend. Regardless of how it all turns out, money could be made in the related stocks as the country ponders the idea's credibility.

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