Note: This article was originally published on December 23, 2015. For the latest updates on Clean Energy Fuels stock check out our ticker page here and for more on Westport Innovations find the ticker page here

What: Shares of natural gas transportation companies Clean Energy Fuels Corp (NASDAQ: CLNE) and Westport Innovations (USA) (NASDAQ: WPRT) both jumped over 10% on Wednesday as energy prices rose.

So what: There wasn't any specific news out about Clean Energy Fuels or Westport Innovations today, but energy markets were very active. WTI crude oil prices were up 4%, while natural gas was up 6% on the day. Meanwhile, futures contracts for gasoline rose nearly 7%, a good thing for the competitiveness of natural gas vehicles.  

Now what: The holidays can bring about crazy trading, so I wouldn't read too much into a single day's move from Westport Innovations or Clean Energy Fuels. But long-term investors should keep an eye on oil and gasoline prices versus natural gas. If gasoline prices rise and natural gas prices stay low, the dynamic works in the favor of natural gas vehicles. But both companies need a much bigger long-term jump in gasoline to really move the needle, not just a single day's bounce around the holidays.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.