Zinc Rich Oil for Flat Tappet Cams

71DodgeDemon340 said
10w-30 is the somewhat the same as sae 30 in that they both have the same heat protection, however the sae 30 weight isnt a multi viscosity oil, the 10w-30 will act as a 10 weight in cold temps and a 30 weight in hotter temps. So if you see any temps colder than say 40 degrees the 10w-30 may be a better choice (Temps in regard to outside temp not engine temp).

Using thinner oil when its cold out takes stress off the oil pump and aids in quicker delivery of the oil in cold temps, using a multi viscosity weight oil gets you the best of both worlds. Plain sae 30 weight isnt reccomended for temps any lower than about 35-40 degrees depending on which chart you go by but the 10w-30 because of the multi viscosity 10 weight cold rating it should be good in temps as cold as 15-20 degrees.

Always remember in multi weight viscosity oils the w in 10w-30 or any other multi viscosity weight stands for winter because it is the cold viscosity rating, the number after is the hot viscosity rating

View attachment 1715262180

I know this is published by gm but there are so many charts out there that all differ 5-10 degrees on the oil rating, this one looked closest to what i prefer as far as oil weights in the temperature ranges. Also if you have a vehicle with a owners manual there should also be a similar chart in it as well

Fwiw im running 15w-50 mobil one and she has no problem starting at 25-30 degrees.

I think your premise is correct, but the post is a little misleading. At least to me.
This is how I understand oil ratings:
The numbers that oil is labeled with represent more than one thing, because the oil has to meet required "standards". So it gets confusing. It's like saying it's a certain shade of blue for SAE-API 10W30...lol.
I understand it as the weight of an oil primarily means that it must provide the protection (load carrying ability) of that given rating. The same number includes the viscosity rating, which is about how temperature affects it. Oil thins, or gets less viscous, with heat. Conversely it thickens, or gets more viscous as it cools.
Viscosity number denotes resistance to flow. So the higher the viscosity number, the less easy it flows at a given temperature. A "straight weight" oil may still thin as it heats. But not by much and must always provide the protection that weight oil has to per the SAE-API. I know of no oil that gets thicker as it heats up, and regardless of it's viscosity if an oil carries a certain weight rating it must provide the performance of that rating. So a "0-50" oil has to provide the protection of a 50-weight oil at 212*. Even if it's not very viscous (as in it's very thin). That being said a higher number rating is about performance, not thickness. In mineral-based oils more protection meant it had to be thicker. No so with synthetics. The first time I ran 5-50 synthetic I was terrified because it was so thin compared to the 20-50 I was running. It still had to provide the performance of 50 weight rating, but it was much less viscous. That's what frees up power: less power loss to pump it and less loss as the parts spin through it while maintaining the protection.
The "0*" or "W" number indicates the tendency of that specific oil to thicken in the cold. 30W is thicker at all temperatures than 10W. 10W is thicker than 0W, etc. So 10W-40 is a 40 weight oil which thins less when cold than 15W40 at zero degrees. It still has to protect to a 40 weight rating at 212*. Even though it's technically thinner.

Here is a decent read about it... I still don't think I "get" all of it but I think I get the gist. http://www.pqiamerica.com/apiserviceclass.htm