• Demand slows for sector as threats loom from Amazon, dealers
  • Stock rout suggests ‘something bigger going on,’ analyst says

O’Reilly Automotive Inc. provided more fodder for this year’s rout of auto-parts retailers, with disappointing sales slamming a sector that’s seen as Amazon’s next potential victim for disruption.

The aftermarket car-parts chain headed for a record plunge after saying Wednesday that same-store sales missed its forecast for the second quarter. O’Reilly’s peers Advance Auto Parts Inc. and AutoZone Inc. also extended declines following weak early-year demand and reports that Amazon.com Inc. plans to mount an offensive on the industry.

Potential threats to the retailers also are coming from the likes of automakers including Ford Motor Co. and dealership groups such as AutoNation Inc. The companies are making an increasingly crowded bet that aftermarket car parts will be in greater demand from Americans that are holding onto their vehicles longer than ever — the average vehicle on U.S. roads is approaching a record 12 years.

“This is the market saying, ‘Wait there’s something bigger going on — the industry is not growing as fast, or…