OK, think we are mostly on the same page with regards to the caveats. The PD pump will, assuming we aren't on the relief, get oil to anywhere pressure lubed at roughly the same time, I think
@Shannow posted a study from the SAE that showed full envelopment time between different oils at different temperatures. However, the places I mentioned, like the pistons and cylinder walls that are splash/spray lubricated, will receive lubrication sooner/receive better lubrication with an oil with a better Winter rating.
This won't change the time it takes for the AW additives to activate, so wear is elevated until they are, hence the claims about start-up (warm-up) wear.
Would depend on the relief pressure set on the pump and whether we are hitting it, so there are some variables we need to account for here. I believe you and Zee covered that in your discussion already however.
Yes, I'd agree with that. It isn't about oil pump or system volume at these locations but how effectively oil can be sprayed/cast on them, where a better Winter rating can provide better lubrication faster.
Yes, pre-lubers ensure that there's oil in locations it needs to be to reduce reliance on existing AW coating build-up, potential removal of, and subsequent wear, while lubricant AW chemistry is not yet active. Wear is still elevated, but it is reduced. This can be improved further by ensuring that the lubricant is also pre-heated, which we also see in some applications.
Yes it is, lol, but I sense that it needed to be mentioned given the direction this conversation has gone, lol.
Don't worry about the quotes, I had no problem reading what was written.
Since we are calling out caveats and have covered the start-up/warm-up wear ones, we should also consider what using lighter base oils means at the other end of the spectrum. Assuming the same family of base oils being used for both products, the 0W-20 is going to have a lighter base oil blend, which means a higher Noack, higher VII content and higher likelihood of experiencing mechanical shear. Depending on the application, this may also increase the likelihood of ring land area deposits (thinking of the Thin Film Oxidation Test and Sequence IIIG or its successors for example). Of course some manufacturers change-up the base oil blend when going with the a 0W-xx. Mobil has a history of using PAO, in varying quantities, when producing these for example.
I apologize in advance for taking this subject even more into the nuance, but member
@Gokhan has produced a calculator where he calculates base oil viscosity and "full shear" viscosity as well as VII concentration:
It's an interesting exercise, though one has to keep in mind that these are estimates.
Great discussion so far! Appreciate the engagement.