This is in the Toyota 3.4L TT. These passages seem awfully small. I’m assuming that’s why 0W20 is recommended. Would the small passages cause any affect with 5W30? I’m sure most if not all manufacturers design engines this way. Those that run 5W30 have no issues.
The effects of 5W30 through small passages
- Thread starter ARB1977
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This is in the Toyota 3.4L TT. These passages seem awfully small. I’m assuming that’s why 0W20 is recommended. Would the small passages cause any affect with 5W30? I’m sure most if not all manufacturers design engines this way. Those that run 5W30 have no issues.
I didn't watch the video but 2 thing come to mind. Heat and pressure would both be impacted.
This is the first time I’ve seen a break down and explanation on this engine. Definitely keeping oci to 5K and use quality oil.
you would assume wrong the difference between a 20wt and 30wt is about 10-20F
so if 5w30 was going to cause an issue a 0w20 thats 20f cooler would cause the same issue.
0w20's only reason is fuel economy.
This tear down was posted Nov 2025.
Toy claims manufacturing debris. 2 manufacturing plants with same cleaning issues is tough to believe.
Other thoughts are spun main bearings due to less than optimal engine design causes debris and engine failures.
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5W-30 is approved for this exact application in the Japanese market. The owners manuals here cannot list anything higher than 0W-20 because that's the weight the test vehicles were CAFE-certified with.
And Toyota just sent recently that 1 viscosity thicker is acceptable due to potential oil shortages.
Question is-where did all the debris come from? Was it caused by too thin oil? Hard to believe Toyota would leave that much junk in a brand new engine! Or is Toyota sharing crankshaft manufacturers with GM?
Where did they say this?
https://bobistheoilguy.com/forums/threads/toyotas-stance-on-using-a-heavier-weight-oil.407147/post-7598329
If it's OK for the service department to use thicker 1 day per week, that was the day I did the same.
The amount of stuff he finds in the oil passages, WOW feel sorry for the owner
It's not all the 20wt oils fault. Combine 20wt oil, plus 10,000mi oil changes, maybe add some fuel dilution or the oil gets too hot and the engine is toast.
Between 20wt and 10k oci I'd say pick one, you don't get both.
Between 20wt and 10k oci I'd say pick one, you don't get both.
2.5 dynamic force is specd 0w-16 and 10k and there are tons of them out there now approaching 200k miles without issue. Personally I don’t but I don’t think this is the issue.
If everything else is perfect. Little to no fuel dilution, oil doesn't get too hot. Did they really only do 20 oil changes to get to 200,000 miles?
Did they use a really use 16wt oil assuming only 20 oil changes to 200k miles? Or did they take it to a shop and where they used whatever they had in the barrel, probably a 9.5cSt at 100c 20wt oil?
Since taking it to an oil change place and getting 10 to 20 more oil and filter changes is a whole lot cheaper than the cost of installing another engine It's just not worth it to push any oil to the 7,500 to 10,000 mile oem oci imo. At least without testing the used oil.
If they take it to the Toyota dealer it did. I am sure many do.
I never said it was a good idea and I even mentioned I don’t myself. I just don’t think thin oil and long OCI are killing a bunch of Toyota engines. The current issues are manufacturing or design issues.
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It struck me as being a what came first question, the debris or the bearing failure ? I think the main bearing configuration is the culprit, too much load on too little surface in a boosted engine. I dont think anyones going to get a straight answer.
Highly unlikely that it's a design flaw in any sense other than they designed something they apparently cannot build in quantity to acceptable quality levels.
It's one thing to pass an engine test with jeweler's sample prototype parts that are in the middle of tolerance and far better than they have to be, it's quite another to pass that test with the worst part that still meets specs.
The elephant in the room here is a confluence of several key factors mostly related to or mandated by regulations:
- Bearings aren't allowed to have lead
- Clearances must be pushed as tiny as as possible to allow the usage of the thinnest oils for CAFE.
- CAFE requires a highly power dense engine with tremendous unit loading and complexity.
- Complexity creates many, many more lubricated surfaces with with slightly different speed/load profiles
- The increasing use of engine oil as a hydraulic control fluid
While I think modern TGDI engines are capable of some incredible performance and are a major advance in tech, I would never consider buying one that had only been in production a year or two. An engine that complex will take many years of warranty data and early life failures to allow them to refine and finish developing what the original product launch schedule did not allow.
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Yep, watched a couple - what a lubricant maze that motor is - and once the bearings become a ‘filter’ …
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