Long as I live! I have met the owner of royal purple and did not like him one bit. But as far as cost prob close to 7.50 a quart. Are you comparing these to Mobil 1? I know mobil is cheaper and the chose of VIper, Cadillac, Mercedes benz and some of the high end Italian sports cars. I just feel that Eneos is the right choice for my Z given my mods. I use Amsoil in my DD integra and it love it. I don't mind paying for eneos and I'm going to do the Blackstone oil report on the first oil change.