Synthetic 10W-30 cSt and HTHS question

[FrankN4]

First let me say that I don't know a lot about 30 grade oils as I have never used them in my personal cars. I have had some "company cars" that were maintained by contract that used 30 grade conventional and I did not like it.

I used a single 40 grade(not XW-40) from 1960 to 1968. I used Castrol conventional 20W-50 from 1968 to 1988. I used Castrol Syntec 5W-50 from 1988 to 1990. I have used Mobil 1 15W-50 since 1990, in everything.

Now that we know my experience with 30 grade, a question.
10W-30 no. 1, GP IV, has a HTHS of 3.26 but a 100C cSt of 12.44.
10W-30 no. 2, GP III, has a HTHS of 3.5 but a 100C cSt of 11.2.

Which would actually give better protection for the engine if bulk oil temp never exceeded 230F? At 230F the cSt of no.1 would be 10.1. The cSt of no. 2 would be 9.2. I have no clue what high point temperatures might be. (I have always considered bulk oil temp of 230, crossing mts with camper pack, far beyond the scope of a 30 grade)

 

[TallPaul]

I would guess the GpIV (PAO) is using a thinner base oil and has more VII. A good GpIII can be close in quality to GpIV. Given the higher HTHS, I would go for the GpIII in this case. HTHS is protection where it most counts. Could boost overall viscosity if you want by adding a quart or two of something thicker.

 

[mechtech2]

Frank - Thick oil like that CAUSES higher oil temperatures.
So it its self defeating, in one sense.
[Because of it's drag when shearing. less flow, and it's thicker boundary layer on parts that need to be cooled.]

 

[FrankN4]

Originally Posted By: TallPaul
I would guess the GpIV (PAO) is using a thinner base oil and has more VII.


Well that makes perfect sense, logical.

I need to find a site where I can learn more, much more about HTHS but searches haven't been very successful as of now.

I have heard that the higher viscosity will cause pumping friction heat but I have also read here on BITOG that synthetic 50 grade only runs about 3F higher than synthetic 30 grade.

 

[MolaKule]

Before the "Science and Technology of Oils and Lubricant Additives" section was openend up to the general public, we had some technical articles and questions such as this:

https://bobistheoilguy.com/forums/threads/hths.41186/

 

[MolaKule]

What vehicle, year, make and engine are we discussing?

 

[FrankN4]

I was just speaking generally MolaKule but lets use the engine in my 2008 Chevrolet Silverado pickup, 4.3L V6, 4 speed automatic, lives between 1500 and a maximum of 3000 RPM. I no longer pull a trailer but I do have a full camper pack taht I slide in the back. Crossing the Great Smokey Mts of Tenn, NC, in 85-95F weather is its maximum load, this about 4 times a year. The rest of the time it is used like a family car. 90% of its life is no load heavier than groceries.

 

[Tempest]

How repeatable are the HTHS tests? What is the +- variation in the test?

 

[FrankN4]

Originally Posted By: MolaKule
Before the "Science and Technology of Oils and Lubricant Additives" section was openend up to the general public, we had some technical articles and questions such as this:

https://bobistheoilguy.com/forums/threads/hths.41186/


Thank you MolaKule. I just finished reading all of the above, Very informative and very educational, and, I might add, very helpful.

WOW...does anyone remember when you could go to a place called a filling station and buy something called motor oil?

 

[FrankN4]

T