Why would oil refineries do that? Unless they are all acting as a cartel to fix prices, it would be obvious that some are more expensive than others for no reas

Why would oil refineries do that? Unless they are all acting as a cartel to fix prices, it would be obvious that some are more expensive than others for no reason. Price fixing doesn't work with price competition. If they are acting as a cartel and coordinating among every refinery, how do you keep that hidden? You can't and the reward isn't worth being screwed by antitrust and all other backlash when you get caught.