Jefferies has upgraded Westport (NASDAQ:WPRT) to a buy, with a $38 price target. In this video, Motley Fool industrials analyst Blake Bos discusses why investors should always treat share-price pops that accompany analyst upgrades as opinion, not fact, and that your personal opinion on the stock -- gleaned from your own research -- should be a factor as well. 

Blake also discusses why Jefferies is predicting that Westport will strongly benefit from an acceleration of natural gas vehicles in the U.S. and China and why this highly speculative stock still has several challenges ahead.

Blake Bos has no position in any stocks mentioned. The Motley Fool recommends Cummins and Westport Innovations. The Motley Fool owns shares of Cummins and 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.