A friend of mine told me that he found a list of which companies use top tier base stock to formulate thier oils. He said it wasn't here so I've been googling and searching here but in an hour; I've been unable to find it. What he'd told me is that Red Line and Motul used top tier base stock while Amsoil,M1, and others; while really great oils use second tier or tier 2 base stocks. Can anyone point me in the direction of a list of the manufacturers base stock used?