5th gen prius 0w8 vs 0w16 discrepancies

I hear you and can see where the confusion (my errors and Toyotas show regarding all this) or misunderstanding is rooted.

the 5th gen prius (engine) was engineered/designed for 0w8 oil. it also left the manufacturing plants filled with 0w8 oil.

when i initially said other regions called for 0w8, i was referring to the factory fill engineering standard used at the plant in Japan.

however, when looking at the printed manuals themselves (the physical books in the glovebox), you are correct: Toyota of Europe and Toyota UK, Japan also listed 0W-16 for the earlier runs.

with that Even in Toyota's home market, the nationwide infrastructure for 0W-8 (JASO GLV-1) was not fully "universal" across every small-town service center at the exact moment of the 2023 launch.

To ensure no owner was left without a service option, Toyota Japan printed 0W-16 in the manual—even though the engine designers had already finalized the car for 0W-8. They did the same thing NA did initially, it looks like.

this is where the "lie/hedge/misinformation" becomes obvious. on many of those early 2023 Japanese units:

the owner's manual said 0w16

the oil fill cap on the engine said 0w8

the radiator support sticker said 0w8

this shows that the manufacturing plant in japan was building a 0w8 car, but the documentation department was still playing it safe with 0w16.

what a country or region decides and then updated environmentally/certification wise and how a car manufacture navigates that is one thing.

what this car and this engine are and were designed and manufactured specifically for oil wise, is another.

that's the end of it for me.

the roots and the fruit have been made clear, for me. the bruises and imperfections of finding clarity on it is par for the course. pretty simple.

enjoy!