Yes,on a copper-brass radiator you really should use radiator paint.On an aluminum radiator the paint used on the copper-brass has the opposite effect.While the aluminum radiator works best left bare,we ain't gonna leave it bright silver in an A.The radiator guy told me to use a light coat of whatever color you want.The biggest thing he told me was to get it clean.The oils and flux residues used in manufacturing aluminum parts is not really cleaned off well from the factory.Nothing readily available to the everyday guy sticks well to aluminum anyway.