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's happening: After climbing 14.4% yesterday, Westport Innovations(NASDAQ:WPRT) stock is up again Thursday. After climbing as much as 16% early in the trading day, it has stabilized at just under 14%, on high trading volume. 

Why it's happening: Much like yesterday, there is no specific news about Westport Innovations. However -- and this is unlike yesterday -- oil prices are up while natural gas is down, so there could be some trading based on the potential for Westport to benefit from that spike in oil. Another likely cause? The percentage of shares held short -- while down relative to most of 2014 -- climbed in January, so today's price jump might be at least partly being driven by short-sellers looking to exit their positions. The old "short squeeze," as it were.

For long-term investors, the price volatility of Westport shares will remain detached from the business while speculation rules the market. Factor in a market cap that just got back above $300 million today, and there's probably going to be plenty more days like this -- in both directions -- until Westport can get its house in order. 

Jason Hall owns shares of Westport Innovations. The Motley Fool recommends and owns shares of Westport Innovations. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.