In Saturday's Fool's Look Ahead, Rick Munarriz questioned whether the Pep Boys (NYSE:PBY) store closures indicated industry weakness or if AutoZone (NYSE:AZO) might shift into a higher gear. Judging by the near-20% leap in AutoZone shares yesterday, Fools got our answer loud and clear.

The auto-parts retailer, nearly 4,000 stores strong, leapt over analyst estimates like one of Santa's reindeer, posting a 16.8% increase in earnings per share for the first quarter of 2008. Revenue rose 5%, while sales of high-margin parts and continued share repurchases helped earnings reach $2.02 per share, compared to the predicted $1.91.

In spite of yesterday's bull run, these shares still closed 7.9% below their 52-week high, posted barely five months ago. Since then, the company struggled through sluggish sales and negative comparable-store sales. At that time, CEO Bill Rhodes promised a brighter future thanks to improving service levels. With same-store sales rising 1.3%, it looks like he made good on his word.

It's hard to say whether economic conditions are putting some wind at AutoZone's back. On the one hand, when consumers start looking to save money, they're more likely to perform some of their own auto maintenance instead of paying for a professional's labor. However, higher gas prices mean fewer miles are driven, resulting in lower maintenance needs. O'Reilly Automotive (NASDAQ:ORLY) didn't miss a beat in its last earnings report, so at least its success doesn't appear to be coming at AutoZone's expense -- not yet, anyway.

Of course, any time a stock surges like this, investors are often left wondering if they've missed the boat. AutoZone now trades at 13 times 2008 estimates of earnings per share, which have grown about 16% annually over the past five years. Since this has always been a well-managed company, I believe investors could pay the current price without feeling they've taken the bait of a suddenly hot stock. However, I expect yesterday's enthusiasm to wane and provide patient investors with a chance to buy in at a small discount to yesterday's close.

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Though Fool contributor Jason Ramage sometimes changes his own oil, he does not own shares of any companies mentioned in this article. Your comments are welcome. The Fool has a disclosure policy.