With your credentials, I respect your expertise... but I'm really struggling to understand this.
For the purposes of conversation, let's use Mobil 1 0W20 and Mobil 1 5W30 for comparison
Mobil 1 0W20
Vis @100C= 8.1 cst
Vis @40C= 43cst
Mobil 1 5W30
Vis @100C= 10cst
Vis @40C= 56.9 cst
Are you suggesting that at 40C, M1 0W20 will deliver superior wear protection to M1 5W30?
Both engine oils are significantly thinner than 43 or 56.9 cst once warmed up, so I fail to see how this matters. Do you have technical papers that I can look into? Thanks.
Your question isn’t apples to apples.
OP was comparing a 0w20 to 5w20. Both are going to be in the 8Ish cst range at operating temperatures. And we’re assuming that OP’s engine, calls for, a Xw20 from the OEM. Which has done testing to certify that product for proper wear protection. In this case, it is perfectly acceptable, arguably, better, to go to a 0w20, instead of using a 5w20.
Now if you’re asking me if I would use a 0w20, in a vehicle that calls for a 5w30 - no. I would not drop viscosity grades unless there was an extreme reason to justify it - such as the oil never actually getting to operational temperatures.
Now, does a 0w30 provide better protection than a 5w30? Yes. In my opinion, a 0w30, again, due to loss of flow from friction, oil pressure vs volume. You might have proper oil pressure - perhaps even high pressure, but you may not be receiving proper oil volume of flow. Which can lead to hot spotting and such in areas.
This is why large industrial systems have pre heaters, or oil heaters throughout their system, especially if it’s a large system.
So, why am I even saying this? Well, let’s start from coldest to warmest.
Cold pour point vs cold flow point vs what is actually safe to run your engine at:
https://www.stle.org/files/TLTArchi...bsiteKey=a70334df-8659-42fd-a3bd-be406b5b83e5
Shill alert: I know the author. (No it’s not me.)
Just because a fluid is rated down to a certain temperature, doesn’t mean it’s safe to run. As well, the viscosity starts increasing quickly, as we get lower than 40c. Which is why (most of us) we prefer synthetics. And also why certain cold tests are so important to OEMs like cold crank.
Why am I not worried about viscosity index improvers?
www.stle.org
There’s a lot of topics covered in that article.
It’s a good read. I don’t have enough time to type out allll the key take away from it on my phone.
Finally:
https://www.stle.org/files/TLTArchi...bsiteKey=a70334df-8659-42fd-a3bd-be406b5b83e5
Low viscosity engine oils in heavy duty applications. They reduce friction, which means you’re reducing wear.
There’s tons of other articles. I’m not sure if TLT is pay walled or not as I’m logged into stle. However, they have a good search engine. You can just type in “engine wear” or “cold flow” and it will pull up articles.
But, increasing the Flow of oil, at “cold start” - which is ambient temperature, can reduce wear significantly. I’ve seen numbers up to 800%. However, that was from a book I have. Which I would need to scan as “proof” - so, I’ll just leave it at can reduce wear significantly.