O'Reilly Automotive Inc. on Wednesday said its profit rose in the first quarter on higher sales and better margins, continuing a trend of 15% or greater profit growth for the past six years. The Springfield, Mo., auto-parts retailer, which recently has been building its distribution network and expanding its store footprint, had projected improved results driven by lower gas prices and wear and tear of older vehicles, particularly those out of warranty, as customers have opted for spending more to repair cars rather than buy new ones.