If auto-parts retailer AutoZone (NYSE:AZO) wants to continue operating in the zone, it's going to have to work on greasing its same-store sales, which, despite all the other rosy aspects of its third-quarter earnings report, remain up on blocks. Comps at its domestic operations once again barely creaked upwards at 0.4% over last year.

While those same-store sales hardly moved, AutoZone just missed boosting revenues to match analyst expectations, reporting sales of $1.47 billion. Analysts expected revenues of $1.48 billion. Profits, though, were strong, rising 5% on the back of selling more private-label Duralast products, which tend to be more profitable for the retailer. Net income rose to $151.6 million, or $2.17 per share.

Per-share earnings profited handsomely from the company's prolonged share-buyback program. Like last quarter, earnings per share jumped 15% as the auto parts company ratcheted up a repurchase of another 1.9 million shares. So far this year, the Motley Fool Inside Value recommendation has bought back 3.8 million shares, providing a hydraulic boost to per-share profits.

As I did last quarter, I continue to wonder whether the stock repurchases are the best use of shareholder money and if it wasn't putting itself in the danger zone by focusing on buybacks. Capital spending continues to decline, down another 16% this quarter and off 13% for the first nine months of the fiscal year. Admittedly, though, and considering its prodigious ability to generate cash, AutoZone's return on invested capital continues to grow, rising 50 basis points to 22.7% over the last four quarter. Its ROIC also well exceeds that of rivals Advanced Auto Parts (NYSE:AAP), Pep Boys (NYSE:PBY), and O'Reilly Automotive (NASDAQ:ORLY).

AutoZone remains a key component of Eddie Lampert's holdings, amounting to 30% of the company's shares outstanding. Lampert's ESL Partners also operates Sears Holding (NASDAQ:SHLD), and many view him as an up-and-coming Warren Buffett with a shareholder letter that rivals the Oracle of Omaha's.

With many analysts forecasting even higher gas prices for the summer, weakness is expected on the road ahead for AutoZone. Yet with more cars on the road (AutoZone considers the number of cars seven years and older to be a key determinant of market growth), it can offset a decline in the other component of future prospects of miles driven. January and February were down, while March was up, and April's figures have not yet been released.

Weather can also play with results, and where retailers were benefiting from the early warmth of March, that reversed with the coldest April in 10 years. AutoZone itself saw the first two weeks of the month create what it termed "disappointing sales."

Cold weather and declining numbers of miles driven may have been what kept same-store sales down. While a flashy new computer system -- AutoZone calls it Z-net -- can making shopping easier for its customers, it's going to have to get them into the stores first to use it. Otherwise, the auto parts retailer's stock will stall.

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AutoZone is a former Motley Fool Inside Value recommendation. A 30-day trial subscription will show you how lead analyst Philip Durell outperforms the market to the finish line.

Fool contributor Rich Duprey does not have a financial position in any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.