Most Citgo stations are independent franchises. Only the refinery stuff is owned by Venezuela. And truth be told, those Citgo stations get their gas from the same fuel terminals that the other stations in the area are getting gas. And those terminals take refined gas from multiple refineries. When the gas is loaded up in the tank truck, then additives specified by the brand are injected into the fuel stream as it is loaded. If a station wants top tier, then the additives are injected into the fuel stream as it goes to the tanker. If another station wants something else, or nothing, added to the fuel, then that is specified at time of loading and fuel is loaded up as the station dictates. The gas in those big, huge storage tanks have no additives, except some basic stuff that is needed for running the gas from the refinery, thru the pipeline, to the terminal.