As far as Europe and Asia and So America vs. NO. America, the ECU programming on VVTi engine will vary with the
oil choice ( KV100) and in open loop where the cams can Advance and Retard many degrees, there is no precise hydraulic control other than the anticipate KV 100 viscosity range.
More viscous oil = higher line/drill pressures will equal more intake cam retard at any given rpm which will push the VE upwards in RPM possibly out of operating range and make the engine feel sluggish and have deleterious and cascading effect on other control systems like ECAT programming, EGR (if external), emission and heat loading, K sense, etc.