** Shares of AutoZone AZO.N fall 5.4% at $3,220 premarket after Q3 results

** The auto parts retailer gross margin slips to 52.2% due to a non-cash inventory charge, despite underlying improvements

** Higher costs and inventory investments continue to pressure margins, prompting retailers to lean more on commercial business for growth.

** The firm, however, posts Q3 rev of $4.84 bln, slightly above estimates of $4.83 bln

** AZO posts quarterly net income of $641.49 mln, or $38.95 per share; analysts on average expected a profit of $36.28 per share - data compiled by LSEG

** 22 out of 28 analysts rate stock "buy" or higher, six rate it "hold"; median PT at $4,300, per LSEG-compiled data

** As of last close, AZO stock up 0.44% YTD