I have a thread about my honda and a different one about my hyundai. When I really think about it I dont REALLY know anything about atf and power steering fluid and I dont REALLY think anyone else does either. I asked about viscosity and how it influences hydrolic fluid, no one knows. I ask about viscosity index and how it affects atf and power steering fluid, no one knows. Maybe I'll just trust the OEM with these choices because honestly I can tell that amsoil atf shifts smoother than z1 when shifting into drive and reverse but I dont really know if its decreasing wear or accelerating it. What do you guys think? I have seen the used oil analysis and seen that OEM atf drops off the table in viscosity but maybe I'll just change it more frequently. I honstly dont know. Z1 vs castrol import vs amsoil or spIII vs castrol import vs amsoil I have no idea and I dont think anyone else does either.