Technically, I made the claim that Toyota wouldn’t recommend a 10k mile oil change interval with conventional oil. That’s a fact, since they never have and do not currently. Pretty easy to draw conclusions as to why.
I agree with that.
Since you’re a scientific guy, this article from “scientific American” seems to think that oil change intervals can be extended with synthetic.
And they may be right. I’m not sure…thus the reason I’m not changing. This whole thread started with the claim that extended oil changes can be acceptable with synthetic. I just pointed out that of the vehicles I owned that still used regular dino oil - said NOT to extend oil change interval even if using synthetic oil. Personally I think it’s a combination of the engine design and synthetic. My wife’s Lexus ES 350 oil recommendation is 5w-30 dino oil and change every 5k miles. Switching to synthetic will not change the interval on that engine.