Retooling a refinery to create a specific oil is a little different than a widget manufaturer using a cheaper razor blade to keep prices down.
Walmart and Mobil may very well have some kind of agreement that allows Walmart to sell Mobil oil for less than Walmart's competitors, but I seriously doubt if that reason is that it's a different oil.
Dustin
"I've contributed alot of good tech help to this site that no one here could have figured out" - JuniorTT 02/15/06