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) fell as much as 10% today as pressure hit oil refiners.

So what: Oil is up big again today, rising more than 3%, and has put pressure on refiners. Another big refiner, Valero Energy (NYSE: VLO), has also been hit hard, so it isn't just a bad day for Western Refining.

Now what: Oil has been cruising higher recently on hopes that Europe will get its act together and the economy will start growing again. Higher oil prices means refiners squeeze less profit from each gallon of gas, and profits will in turn be lower. I don't think oil is done running higher, and therefore I would avoid buying refiner stocks right now.

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