Use Zerex 50/50 pre-mixed anti freeze and bring the coolant level up to about 3/4 to a 1/2 inch of the black reservoir top when viewed from the side. You can see the liquid level thru the white colored plastic. You can also look down through the fill top and see a whit plastic rib in the rear of the reservoir. The top of the rib should remain visible above the coolant level.