O'Reilly Auto Parts, now combined with CSK Auto, is the third largest auto parts retailer in the US. The combination of O'Reilly's midwestern and southeastern foothold, along with CSK's dominance in the western US, has created a stronger, more. Auto Accessories,Air Conditioning,Battery & Accessories,Belts & Hoses,Body & Trim,Brakes,Charging & Starting,Cooling & Heating,Engine Parts & Mounts,Exhaust,filters & PVC Valves,Fuel & Emissions,Ignition & Tune-up,Lighting & Electrical,Oil