I suspect that motor oil is much like gasoline in this sense. When buying gasoline at the port, the transport driver dials in his information and the grade and brand of fuel he wants to load. The barge came in with immense compartments filled with regular and premium fuels. As the fuel is dispensed into the transport the additive package is also dispensed and that additive package was determined by the brand selected by the transport driver. Therefore it seems to me that the basic motor oil product could be manipulated just before packaging and additives specified by the private label purchaser could be made there.
You pose a very naive question. Your answer implies that there is no difference between the two filters. Purolator could very easily build a filter to comply with specifications given them. The filter media could be totally different and 500% better than the standard media used in their own filters. I know of one manufacturer who makes and packages a product identical to the one generally sold under their name, but is of a very inferior quality for sale in a discount environment. I know thatâs a dumb decision on the manufacturerâs part, but thatâs what they did.