I’m really interested to learn more about your research, because these findings are interesting. If you can share some of your methodology it might shed light on the confusing findings.
The market observation I'll grant you. "different markets don't have identical motors with different tolerance" is a fair point, and the same engine getting 0W-20 here and 5W-30 in Europe or Australia hasn’t been well explained anywhere that I’ve seen. That's an argument about why the recommendation differs. It isn't yet an argument about what the oil is doing in the sump. So:
You wrote "HTHS is what causes the oil to break down BEFORE 10K." Can you walk me through that mechanism, and how you measured it? HTHS is a viscosity measurement taken at 150°C at a shear rate of one million reciprocal seconds. It's a number that describes the oil, the way a torque spec describes a bolt. What's the pathway you observed by which a measurement (HTHS) causes degradation? Oxidation, nitration, fuel dilution, TBN depletion, and permanent VII shear are processes. Which process are you actually pointing at when you state HTHS causes the oil to breakdown early?
Related: you list "~2.5-2.7 with 20 weights." SAE J300 sets the HTHS minimum for the SAE 20 grade at 2.6 and for SAE 30 at 2.9. A licensed xW-20 at 2.5 doesn't exist. Where did your 2.5 come from?
On "this breakdown typically occurs in the 6-7000 mile zone predictably," and "as was shown very nicely by analysis on this forum": how many samples, across how many engine families? And the one that matters more, what did the 30-weight UOAs from those same engines, same mileage, same driving pattern show? And more importantly, as asked above, what exactly did you observe break down? Without that comparison I don't see what the 6-7000 number is measured against.
"the oil is still 99% doing its job." 99 percent of what, and how did you measure it?
On the interval: you say moving to a 30 makes it "very safe to extend oil change interval to at least 7500 miles." What does the 30-weight have more of? Same detergent, same antioxidant package, same starting TBN, same dilution rate in the same engine. If viscosity grade sets the safe interval, what's the mechanism your research uncovered?
"has NO downside." What did you measure to establish that? Did fuel economy delta, cam phaser response time, and oil temperature all get measured as a part of your research? Phasers, chain tensioners, and AFM/DoD lifters are hydraulically actuated and calibrated around a viscosity, so I assume they were all carefully considered in your research.
"It is still the world standard." Japan is on 0W-16 and 0W-8 factory fill. Which standard are you talking about?
The filter point I think is well-proven, at least for cellulose media.
1. The most important point is listed first. Plain and simple. Same motor uses different oils in different markets. Lots of CYA in the manuals too.
2. I have watched MOG, Bob is Oil guy, petrochemical engineers of all sorts etc for years. This is what they say. HTHS is a far more important data point than "grade". I am to be corrected on the 2.5. It is 2.6. BYW, the beloved Toyota oil has a bare minimum as it is 2.6-2.7. No thanks
3. One of the guys on this forum ??Page?? did a very nice analysis and these were his findings. I then looked elsewhere and see the same findings. 0W-20 limps to the finish of a 10K interval.........
4. 99% -50% whatever. At 5K it is still working.
5. Longevity of oil and HTHS go hand in hand. Please don't quantify this with YOUR hands...messy.
6. I just drove up with 5W-30 and a frsh filter at same speed, relative same temps etc as last month with 0W-20. I got the best mileage ever. So, again, my research has shown +/- .1 mpg improvement based on the thinner oil. 23.4mpg. Prior to this I got 23.1 once and ??22.7 a few times.
Finally, your discounting my research suggests you think all the recent motor failures on multiple brands over the past decade or so , many that had recommended 0W-20 oils, some on motors that previously ran 0W(5w)-30, has no correlation to oil...but of course those engineers perfectly planned for those failures? MY GUT OPINION NOW. Ask those engineers if they would have preferred to stay with 5w-30. Ask them if CAFE standard pressures played a role in succumbing to the thinner oils. Ask them if they think thinner oils and high heat generating turbos are good bedfellows.
Japan is a bit part of the problem lately. Nuff said with their standard.
A question I did not know the answer to but am suspicious about. What country first stopped recommending break in oil changes? I lied and checked this from several sources. It was Japan! OOPS!! Might have saved a whole bunch of motors. The recall and manufacturer campaign codes for the affected 2024 Toyota Tundra V35A engines are
25TB14 and 25TA14, registered under NHTSA recall number
26V320. Japan is not perfect.
I am a relatively intelligent individual. I have watched AND read numerous articles, videos, shows on oil. I got interested around 1999 when I got my SVT Cobra early in the synthetic era (for me). I previously owned turbos Impulse RS, RX-7s) and saw first hand what they did to oils. I currently track my 2018 Alfa Romeo 4C with its 1.7 T motor. My Lotus were all SC'd. I have experienced carbon on a ring resulting in oil burn under WOT conditions. I have communicated with Lake Speed on the topic. I have tried Valvoline P&R and been shocked at what it can do. No longer burn oil. Dipstick shiny as new. Put light in filler holes, damn clean looking now. I read, watched, asked and tried............it worked. Aside, but....And yes, motor rebuilds......
Here is my take again. If our Toyota motor was NOT a turbo, I'd be much more likely to leave the 0W-20 alone. Just like those Corollas etc running 0W-8 and or 0W16.
But I know turbos cook oils and to a slightly lesser extent superchargers. I had my 2 Range Rovers. The 2016 3.0Sc never went past 10k even though intervals could be longer. At least it was 8+qts! Just looked like old oil. My 2021 RR had the 3.0tt motor and it had a 9+qt capacity. Again 10K max intervals. Man that oil was gnarly on the 2021 that ran on 0W-20. Black! Totally subjective but anyone that has changed oil for 50years knows the difference. My old Impulse RS 1.6 T motor existed before synthetics and the oil looked jet back and dead at 3K miles! Oil coming out of turbos ALWAYS looks more abused. Turbo motors sound more different with fresh oil than non forced induction motors.....HTHS strikes again.
Peace. I simply stated my plans. I have changed based on MY research. The new oil (5W-30) sounds better and makes our motor smoother. I have seen , ironically better mileage. I will hold further judgement on mileage till I rack up more trips. I just went out with wife and started car she drove all last year. Even she says the motor sounds quieter and smoother. All I asked was "what do you hear?" In conclusion, Engineers can fuck up too.......
Our Toyota only takes 5.0qts. Less oil IMHO working harder in a smaller yet higher output motor based on size. We all know, at least those of us that watch gauges, how much time it spends boosted...........