From heating homes to fueling vehicles, natural gas has been making strong inroads over the past decade.

In fact, when oil prices were high, the cost of operating a truck on diesel fuel was as much as 60% more than the cost of operating the same vehicle on natural gas!

Clean Energy Fuels (CLNE) jumped on the opportunity provided by the gap and built a plethora of dry and liquid natural gas facilities across the country.

Now that oil is cheap, however, the difference has narrowed substantially, to around 30%.

The effect on CLNE's shares has been quite pronounced. Shares were down more than 60% since December 2013.

But don't sell your natural gas shares just yet. The fuel's inherent qualities are standing up to the “Black Beast.”

In Your House and on the Road

The movement towards natural gas is most evident when it comes to heating and transportation.

When oil prices were at $100 and heating oil prices were above $4.50 per gallon, it cost twice as much to warm an oil-heated home than one using natural gas. With the record-breaking winter we had last year, oil-heat homeowners were looking at their natural gas neighbors with envy. That gap has narrowed as oil prices have plunged, but natural gas-powered heat is still cheaper.

There are other benefits besides price, too. Unlike heating oil, which is delivered, natural gas is always “on.” And oil furnaces tend to leave a less-than-desired smell wherever a furnace is located.

Ultimately, though, it's the cost/benefit that counts. Oil prices might be lower today, but history shows that natural gas tends to be consistently cheaper over time and less subject to shocks, outside of short-term issues related to weather.

Oil, on the other hand, is impacted by everything from weather to politics 8,000 miles away.

On the transportation side, as oil prices continue to drop, truck engine manufacturers may pull back on their production of natural gas engines. However, they won't simply stop production.