Check the bottom of the bottles next time you're in the store. It CAN vary from jurisdiction to jurisdiction - basically they go with whoever is "cheaper" in the area (to include freight/travel costs).
Here most of the generics are WPP (warren Oil) due to their distribution center just a cpl states north of us (North Carolina if I recall? But could be wrong).
Warren Oil Company,not Warren Performance Products makes or did make the Advance brand.Warren oil is based in North Carolina and bought the Coastal brand some time ago.WPP is in Nebraska and makes Super Tech and have their own brands of oil,Mag1 and Accel and other products under the Polar name.These are not the same companies and are not in any way connected.