* 3rd-qtr earnings $7.27/share vs est $7.21
* Revenue rises 4.5 pct to $2.21 billion
* Same-store sales fall 0.1 pct
May 21 (Reuters) - AutoZone Inc, the largest U.S. auto parts retailer, reported a better-than-expected quarterly profit as U.S. customers undertook car repairs after a prolonged winter.
The company, which faced weak demand a year ago as a warmer-than-usual winter resulted in less wear and tear to vehicles, said there was a noticeable improvement in its performance, mainly in the U.S. Northeast and Midwest in the final four weeks of the quarter.
AutoZone said in February it would grow faster in the second half of the fiscal year as it expected the severe winter to drive up auto repairs.
Gross margins rose to 51.8 percent in the third quarter from 51.6 percent a year earlier, the company said on Tuesday.
AutoZone, which competes with Advance Auto Parts Inc and O'Reilly Automotive Inc, said sales rose 4.5 percent to $2.21 billion, in line with analysts' expectations, according to Thomson Reuters I/B/E/S.
Same-store sales fell 0.1 percent.
Net income rose to $265.6 million, or $7.27 per share, in the third quarter, from $248.6 million, or $6.28 per share, a year earlier.
Analysts had expected earnings of $7.21 per share.
Memphis-based AutoZone's shares closed at $409.05 on the New York Stock Exchange on Monday. They have risen over 10 percent in the last three months.