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.