Best oil? 0w20 or 5w30

i am sure Toyota could have reached the mpg demands without using a special oil. The engine tolerances were designed for 0w-20 oil so you should use that. Some of the latest engines are now designed for 0w-8 oil. I used 0w-20 oil for several years in my 2017 Prius with no issues.

 

The info I have heard from Toyota is that 0w20 is filled at factory for the initial virgin period and then replaced with 5w30 - atleast in Europe.

 

Toyota did that fir some models when the factory oil was not readily available in some countries. For instance, on my 2017 Prius,. rumor as it had 0w-16 but the US manual said 0w-20 because 0w-16 was not widely available.

You should go with the recommendation from the owners manual for your country. In most cases, it is available online.

 

Engines receives its most wear during startup; before engine oil makes it to where it's needed. Newer engines has tighter tolerances and smaller oil passages; mainly due to experience and better tooling. The oil itself is full synthetic and more uniform than old school dino oil and also resist stress & thermo breakdown better. The Prius engine starts and stops more often than a regular car engine and once the engine is running; it's mechanical parts are floating on a cushion of motor oil.
The majority of Toyota motors reach 200K trouble-free miles, if you exclude the gen3s; so I think the Toyota engineers know what they're doing. I wouldn't second guess them with that track record.

 

I doubt this was made because the oils where not readily available. A new motor needs special care. Sounds like a rumor indeed.

Anyhow, 5w30 is recommended on eu models. Always check the oil fill cap for the recommended type. And use a quality filter, OE is cheap.

 

I've toyed with switching from 0W20 to 5W30, for one oil change at least, see how it goes. Or hey, 5W20?

It does stretch credulity, the steady march towards thinner oil, and the disparity in policy: different countries, different oil weight recommendations, with the same engine.

 

FWIW; I'd be hesitant to go with a heavier oil in a cooler climate, anywhere that snow sticks to the ground. Anyone who has lived in snow country remembers to go to a thinner oil in the fall-winter months. If your young enough to only see multi-grade oils, you won't know what I'm talking about.