3% Fuel in 1st Oil Change at 1300 miles 2024 XLE

The Dynamic Force engines we see in North America include:
M20A-FKS(2.0L I4 non-hybrid)
M20A-FXS(2.0L I4 hybrid) - this is the gen5 Prius engine(both HEV & PHEV)
A25A-FKS(2.5L I4 non-hybrid)
A25A-FXS(2.5L I4 hybrid)
T24A-FTS(2.4L I4 turbo)
V35A-FTS(3.4L V6 turbo)

The two turbo engines(T24A-FTS & V35A-FTS) use 0W-20 because of extra abuse of the oil to cool and lubricate the turbo. Of the non-turbo engines, all have switched to 0W-8 for at least some vehicles except the M20A-FXS like in our Priuses. I expect the M20A-FXS switching to 0W-8 is only a matter of time.

I guess I'm trying to say that I have no qualms about using 0W-16 year round since the overall engine design has been thoroughly validated down to 0W-8.

 

As I was typing this, I did sort of change my mind. If the belief the 'Toyota is doing this solely for emissions, and fully allow other viscosities in other countries', then it just begs the question that why they do even reference 0w16 and 0w8 in other countries. If the "EPA is forcing them to" is true, then they'd just 100% recommend 5w30 or 0w40 or whatever in 'other non US countries'. The way it's written in say, the UK's manual:

Owner's Manual | Toyota Europe (toyota-europe.com)

It still directly references 5w30, but still 'recommends' 0w16. So it goes down a rabbit hole: If Toyota did truly think we should be using a thicker oil, would they take the effort to recommend 0w16 'everywhere'? Admittedly, the US is a large market, but intentionally kneecapping your motor with crappy oil doesn't seem like a fantastic idea.

Anyways, given how it's written in different countries, I assume there's a fairly wide berth of oils you *CAN* safely use; 5w30 is 100% referenced in other countries. Whether or not it really 'matters' is probably the more important question, which is hard to answer....

 

Markets vary. Synthetic oil in Europe is 100% synthetic. Toyota calls for what is midgrade octane in the US for the Prius there. Drivers there had to put in more effort to get a license, so might be better informed about cars in general.

While the UK manual references 5w30, it doesn't say anything about when to use it. The text is mostly like the US version, "If SAE 0W-16 oil is not available, SAE 0W-20 oil may be used. However, it should be replaced with SAE 0W-16 at the next oil change." Then there is the bit about higher viscosity might be better for high speeds or engine loads.