What happened 

Shares of natural gas distributor Clean Energy Fuels Corp. (NASDAQ:CLNE) were down 10.2% at the close of trading Monday on no real news. Shares were down as much as 11.8% in early morning trading, and were down by high single digits for most of the day. 

So what

Oddly enough, crude oil is trading slightly higher today with WTI crude up 0.3% and Brent crude up 1.5% on the day, which is usually a bullish sign for Clean Energy Fuels. Natural gas is also down 1%, which should lower input costs, another factor that usually pushes the stock higher. 

Tanker truck on highway.

Image source: Getty Images.

Sometimes stocks trade on momentum or factors that have nothing to do with fundamentals, and that appears to be what's happening today. Shares were also down double digits last Thursday on an analyst downgrade, so this could be momentum from that move as well. 

Now what

Not a lot has changed with Clean Energy Fuels in the past week, but the stock has been dropping sharply, giving back over half of the gains for the year. Nonetheless, shares are still up 40.6% on the year, so it's been a strong year for the stock. 

Rather than watching the ups and downs of trading on any given day, I would keep an eye on Clean Energy Fuels' performance on a fundamental basis in coming quarters. Volumes were flat in the first quarter at 85.1 million gallons delivered, which management needs to improve upon if the company is going to generate long-term profitability. More than any analyst decision or momentum swing, it's a fundamental improvement that will drive the stock.