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 Western Refining (NYSE: WNR) are climbing 15% higher today after a hedge fund announced a big stake in the company.

So what: Appaloosa Management, a hedge fund managed by David Tepper, opened a 2.8 million-share position in Western Refining during the second quarter. The fund made a big move into refiners during the quarter, adding to stakes in Valero Energy and CVR Energy as well.

Now what: We don't know exactly what Tepper is seeing in refiners, and buying just because a hedge fund is buying isn't wise. But if you're looking at Western Refining's forward P/E ratio of six and seeing a lot of value, it may be time to jump in. Don't follow hedge funds blindly, but take it as an opportunity to do some due diligence and see whether Western Refining is the right investment for you.

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