5th gen prius 0w8 vs 0w16 discrepancies

I think this was mentioned in a thread before. Dug deeper and called Toyota Of America. Apparently the 26 engine is identical, of course, to the 23 engine.

Although the 26 engine verbage in the manual clearly states 016w may be used for one cycle and then immediately go back to 0w8 consistently.

Strange. Seems to be begging for a larger issue, even if possibly only technical.

Apparently the same engine on non north American sold vehicles with this engine, Prius 5th gen.. always recommended and requires(?) 08w oil, as per the manual. And for the 26 they finally updated the verbage.

I don't want to be putting in the wrong oil due to some timing and certification North American issue.

thoughts?

I understand one can change their own oil etc

hmm

 

Toyota of America - on the phone - said the engines are identical. Mayne they are wrong, hmm? Want to share the evidence?

infact, every non north american 5th gen prius from day one called for 08w oil.

when the 5th gen prius launched there, the manual and the oil cap both said 0w8. the engine is the m20afxs and it is identical worldwide.

the proof is in the global part numbers. toyota uses the same oil pump and the same engine bearings for a prius sold in tokyo as they do for one sold in los angeles. japan has had 0w8 at every gas station since 2020, so they never had to "ease" into it like the west did.

north american manuals only mentioned 0w16 because 0w8 wasnt in us warehouses or certified legally yet. everywhere else, 0w8 was the standard from the first car off the line, and still is.

the japanese proof?

toyota japan launched the 5th gen prius (model code x60) in early 2023. the official japanese owners manual lists 0w8 (jaso glv-1) as the standard factory fill.

toyota developed 0w8 specifically for the japanese market years ago. they officially published the technical engineering paper for it in 2020 (sae paper 2020-01-1425).

by the time the 5th gen prius arrived, 0w8 was already the default oil for the m20afxs engine in japan.

the european proof?

toyota europe and toyota uk released the 5th gen prius exclusively as a plug in hybrid. the technical press packs and manuals from launch confirm the use of ultra low viscosity oil.

european manuals state 0w8 is the best choice for fuel economy and cold starts.

because europe and japan already had 0w8 on store shelves, they didn't need to put 0w16 on the oil cap as a "temporary" fix like they did in the united states.

why the us was different?

the only reason north american manuals mentioned 0w16 at launch was because the american petroleum institute (api) had not yet finished certifying 0w8 for us sale. the car was ready for 0w8, but the american oil companies weren't.

every 5th gen prius engine is built in the same factories with the same clearances. since those factories are in japan, every single one was filled with 0w8 before it ever touched a boat.

edited for grammar, woops

 

yes, the conclusion is all the 5th gen are designed specifically for 08w oil, regardless of poor NA liability, certification convolution and ill timing.

to be extra clear, albeit repetitive, every 5th gen prius is designed specifically for 08w oil. and as the 2026 manual states, 016w should only be used as place holder for at most 10k miles and then immediately back to 08w.

the reason I brought it up initially here was for context, curiosity, transparency and consumer discourse etc.

good question, thanks for asking.

 

... it's in every single manual for every single 5th gen car except NA version (explained above) before 2026, which all have the same exact engine.

the car was designed for 08w. the new 2026 NA manual finally reflects the required 08w oil for our engine.

Toyo of merica' did also confirm ALL this.

(even if they didn't - which they did - even a low surface research into it all, confirms all the simple details)

I understand your question was direct and perhaps my wording confused or misled you to think otherwise. Here, I've attempted to make it crystal clear, out of respect for your initial question.

Joe Blow did say those things when they looked in to our engine and explained the discrepancies. Also, whatever you prefer to presume or conclude is upto you of course. Enjoy.

Like for anything, I would encourage someone to research things as important as required oil for their engine, themselves. Check the manuals, check the timelines, call Toyota of america and other Toyota international agencies if needed. That's what I did.

I appreciate your initial question.

 

Also, in this case, it's not a complicated path to confirm, which is good and provides clarity for anyone doubting the reality about all this.

And it really doesn't matter what someone who answered the call at Toyota of America says or not. I shared it because it was interesting and it happened.

They could be wrong. The NA manual for 23, 24 and 25 was wrong on oil... even I could be wrong, of course.

Anywho: if this were a case, I believe the facts are clear.

It also doesn't matter what NA manual said for 2023 2024 2025, because it was incorrect from the start. Which was explained, indepth.

A person might say, how can you rely on the international manuals recommendation/requirement for oil when they got the NA manual wrong. The answer to that has all been explained. And anyone that looks to confirm will find the same facts. How they interpret those facts is up to them.

It matters what the manufacture calls for this particular engine and what this engine was designed for, oil wise. Everyone has a different lens, I prefer to go to the roots of an issue to find out why something is misleading or convoluted.

5th gen Priuses require 0w8 oil. 0w16 may be used in a pinch for 1 cycle, as per the manufactures overwhelming instruction for all other regions, with the same exact engine.

The delay in certification and desire to sell the car before certification in NA - regarding the 08w oil - led to all this convolution and confusion.

Simple.

I'm not saying I'm perfect or right on this. I'm saying what the facts are and what Toyota of America told me and what I interpret that as.

 

Some more interesting thoughts..

While some of the 2025 Corolla and Camry models with the same engine finally show 0W-8 in their U.S. manuals, the 2023, 2024, and even 2025 Prius manuals in North America have largely remained stuck. We won't see a "clean" manual update for the Prius until the 2026 model year, simply due to how slowly Toyota of North America (TMNA) updates their printed documentation compared to their engineering specs.

The engine in (my, early manufactured) 2023 Prius is the M20A-FXS. If you look at the exact same engine in a 2025 Corolla or a 2025 Camry, the manual now explicitly mandates 0W-8. The Prius manual is an "orphan" in this regard, Toyota updated the oil cap and the production line, but the legal/documentation team for the Prius specifically hasn't caught up.

If your radiator sticker and manual both incorrectly say 0W-16, check in the following spots:


The VECI QR Code: Scan the QR code on that same radiator support sticker (if there is one) This often pulls up the EPA Certification data for your specific VIN. Because the M20A-FXS was certified globally using 0w8, the digital record often contradicts the printed text on the physical sticker.

The "J-VIN" Identity: Open your driver’s side door and look at the VIN plate. It starts with a "J". This confirms your car was built in the Tsutsumi plant in Japan.

In the Japanese Service Manual for that exact plant and build date, the only oil listed for the 5th Gen Prius is 0w8.

Engine Serial Number: There is a small flat "shelf" on the engine block (usually near the front where it meets the transmission) It is stamped M20A. This is your proof that you have the Dynamic Force engine.

Toyota of North America likely kept 0W-16 in the Prius manual for 2023–2025 to avoid warranty claims from people who couldn't find 0w8. If they "required" 0w8 in the manual but didn't have it at the dealerships (which was the case until mid-2024), they would be legally liable for service delays.

There was a Toyota tech tip issues.

If you go to a dealer, they will look at your VIN and the "wrong" manual (unless you have 2026 one, I believe) and give you 0W-16.

To get what the designers intended, you should, reference tech tip T-TT-0692-23

This is the internal Toyota memo that tells technicians 0W-8 is the "new" standard for these engines. (also, from day one that was the required oil for this engine, regardless of Toyotas... b.s. with all this)

Request Part #00279-08QTE, specifically ask for this oil by part number.

In the global engineering data for the 5th Gen Prius (Model Code ZVW60/MXWH60), aka our exact engine, the "Lubrication System" section explicitly defines the design requirements.

Design Viscosity: SAE 0W-8

Certification Standard: JASO GLV-1 (This is the only global standard for 0W-8).

The documentation notes that the engine's electric VVT-iE and variable discharge oil pump are calibrated to the specific flow rate and pressure curves of 0W-8.

Using 0W-16 creates a "drag" that the ECU-controlled pump must compensate for, which deviates from the engine's 14.0:1 compression efficiency map.

Curiously, they created an entirely different problem.

The car requires 0w8 oil.

*elmo shrug*