A passive method for conserving fuel vapor by connecting the ullage space of the liquid fuel storage tanks to a bladder in a vapor conservation tank; connecting the ullage space of a liquid fuel delivery vehicle to air space of the vapor conservation tank, external of the bladder; delivering liquid fuel from the delivery vehicle into the liquid fuel storage tanks, the liquid fuel displacing fuel vapor from the storage tanks; delivering displaced fuel vapor into the bladder, the delivered fuel vapor inflating the bladder and displacing air from the air space of the vapor conservation tank, external of the bladder; and, thereafter, over time, delivering fuel vapor from the bladder into ullage space of the fuel storage tanks, replacing the volume of liquid fuel delivered from the fuel storage tanks into vehicle fuel tanks. A passive system for conserving fuel vapor is also described.