Variation of HT/HS values within the same grade

[The Critic]

Let's use 5W-20 as an example:

Oil A: HT/HS= 2.67, VI= 153
Oil B: HT/HS = 3.27, VI= 140
Oil C: HT/HS = 3.0, VI=147

All three oils are "full synthetic" 5W-20 products with a Vis @40C between 50-53 cSt, Vis@100C between 8.7-9.0 cSt.

How can there be such a significant difference in HT/HS values?

 

[BMWTurboDzl]

different base oil blend combined with different dosage of VII?

 

[userfriendly]

Mobil has an example in their blending chart of a 5w30 with a HTHS of 3.7
Most of the 10w30 HDEOs are in the 3.5-3.7 range.
An SAE 30 just under the 12.5 limit, group I base oil is over 3.8

 

[The Critic]

Mobil has an example in their blending chart of a 5w30 with a HTHS of 3.7

Can you provide a link to this blending chart? Thank you

 

[tyman]

There was a good thread, iirc by Gokhan, a few months back that talked about how there are W-20 oils with a higher HTFS than some 5W-30 or even some -40s.

Rethink and understand SAE viscosity: a 0W-20 can be thicker than a 0W-40 or 5W-40

This is my conclusion about the SAE J300 viscosity specification: It is obsolete and does not give the full picture. SAE J300 was updated in the mid-1990s to correct inherent problems associated with it by introducing the HTHS viscosity, which is measure at 150 ℃ and a shear rate of 10⁶ s⁻¹. At...

bobistheoilguy.com

 

[High Performance Lubricants]

different base oil blend combined with different dosage of VII?

This

Also the DI pack can contribute as well.

 

[RDY4WAR]

Base oils vary in density and pressure-viscosity coefficient, which affects the dynamic viscosity and thus the HTHS. Blends of different base oils are used to achieve desired results.

 

[userfriendly]

Can you provide a link to this blending chart? Thank you

https://www.exxonmobilchemical.com click on the second row left square, girl in the lab coat and purple shirt "synthetic base stocks".

Then scroll down and download the; synthetic_lubricant_base_stocks_formulations_guide_en_2017 pdf

 

[Jetronic]

Let's use 5W-20 as an example:

Oil A: HT/HS= 2.67, VI= 153
Oil B: HT/HS = 3.27, VI= 140
Oil C: HT/HS = 3.0, VI=147

All three oils are "full synthetic" 5W-20 products with a Vis @40C between 50-53 cSt, Vis@100C between 8.7-9.0 cSt.

How can there be such a significant difference in HT/HS values?

HTHS viscosity is inversely proportional to viscosity index.... so, viscosity index improvers at play would be my guess.

 

[The Critic]

HTHS viscosity is inversely proportional to viscosity index.... so, viscosity index improvers at play would be my guess.

Probably an oversimplification of the scenario, but it sounds like:

Lighter base oils, more VII = higher VI, lower HT/HS
Heavier base oils, fewer/no VII = generally lower VI, higher HT/HS

I assume that you can only have a certain amount of variation in the final outcome if you are staying within the prescribed J300 boundaries.

 

[Jetronic]

Probably an oversimplification of the scenario, but it sounds like:

Lighter base oils, more VII = higher VI, lower HT/HS
Heavier base oils, fewer/no VII = generally lower VI, higher HT/HS

I assume that you can only have a certain amount of variation in the final outcome if you are staying within the prescribed J300 boundaries.

Especially when going to lighter base oils. But that's exactly why those boundaries are there.

 

[userfriendly]

Especially when going to lighter base oils. But that's exactly why those boundaries are there.

A 10w30 FA-4 with its 3.1 HTHS limit is a good example of that. A relatively low KV100C and VI yeilds a 3.1 HTHS at a low cost.

 

[OVERKILL]

Base oils vary in density and pressure-viscosity coefficient, which affects the dynamic viscosity and thus the HTHS. Blends of different base oils are used to achieve desired results.

And different base oils can be used to manipulate these characteristics and increase the VI in a finished lube, like mPAO, I was recently educated on by a certain somebody we both know

 

[RDY4WAR]

And different base oils can be used to manipulate these characteristics and increase the VI in a finished lube, like mPAO, I was recently educated on by a certain somebody we both know

I feel like mPAO doesn't get enough recognition. You'd be hard fought to find a more shear stable base oil that also extends the drain interval, improves foam/aeration resistance, greater OFT, and lower friction.

 

[4WD]

And different base oils can be used to manipulate these characteristics and increase the VI in a finished lube, like mPAO, I was recently educated on by a certain somebody we both know

Thought mPAO was on the thicker side and a bit expensive for D1.3 lubes and the like … used in industrial lubes etc …

 

[OVERKILL]

Thought mPAO was on the thicker side and a bit expensive for D1.3 lubes and the like … used in industrial lubes etc …

Yeah, it's not cheap, but it can be used as a VII basically, to increase VI.

 

[4WD]

Yeah, it's not cheap, but it can be used as a VII basically, to increase VI.

Right - lower dose is my understanding … Heavy industrial gearbox use they can pile it on …

 

[OVERKILL]

Right - lower dose is my understanding … Heavy industrial gearbox use they can pile it on …

Yup, basically as an "adjuster" fluid in PCMO/HDEO, they can use it straight up or in much higher quantities with industrial stuff that calls for higher visc.