Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of natural gas fuels specialist Clean Energy Fuels (Nasdaq: CLNE) powered up to a 13.4% intraday gain on moderately heavy volume.

So what: Westport Innovations (Nasdaq: WPRT) and a subsidiary of Royal Dutch Shell (NYSE: RDS-A) just announced a joint project to promote the use of liquid natural gas in heavy-duty commercial vehicles. Shell mainly produces the fuel, Westport builds LNG-friendly engines, and not-so-innocent bystander Clean Energy Fuels may get to build refueling stations.

Now what: It's exciting to see cleaner and more sustainable fuel technologies slowly making their way into the mainstream. Yeah, LNG is still a petrochemical product just like the oil, diesel, and gasoline we all know and loathe, but a less-exploited and somewhat more eco-friendly one. If Shell and friends can make this work for commercial vehicles at first, we'll have a low-cost alternative to gas-and-battery hybrids for the consumer market soon enough. When the natural gas runs out, let's just hope we'll have cold fusion reactors in every home already.