AutoZone Inc.'s (AZO) fiscal third-quarter profit rose a better-than-expected 9.5%, helped by strong sales of auto parts to cost-conscious home mechanics and commercial repair centers.

AutoZone shares rose 2.5% premarket to $166.95. The stock through Tuesday is up 17% on the year.

While the recession has put Detroit auto makers on life support, auto-parts companies are holding up as cost-conscious consumers fix old vehicles instead of buying new ones. The closing of hundreds of dealerships by Chrysler LLC and General Motors Corp. (GM) is expected to drive even more business to replacement-parts companies and auto repair garages.

For the quarter ended May 9, the nation's largest auto-parts retailer reported a profit of $173.7 million, or $3.13 a share, up from $158.6 million, or $2.51 a share, a year earlier. Net sales rose 9.3% to $1.66 billion, with U.S. same-store sales up 7.4%.

Analysts surveyed by Thomson Reuters were expecting earnings of $2.89 a share on revenue of $1.61 billion.

Gross margin was flat at 50.2%, as benefits from lower fuel costs were offset by promotions.

When gasoline prices were at record levels, consumers were postponing all but the most necessary car repairs, pressuring parts-retailers' profits. But the tumble in gasoline prices since mid-2008 and broader economic weakness has helped send customers back to those stores. Last week, AutoZone's biggest rival, Advance Auto Parts Inc. (AAP), reported a bigger-than-expected 14% earnings jump.

-By Mike Barris, Dow Jones Newswires; 201-938-5658; mike.barris@dowjones.com