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Automated calculator for the A_Harman index, VII content, and base-oil viscosity #5423638 05/07/20 08:05 PM
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Gokhan Offline OP
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I have now fully automated my A_Harman index, effective VII content, and base-oil viscosity calculator by building in the ASTM D341 viscosity - temperature relation (Walther formula) into the spreadsheet.

If you want to calculate these values for an oil, you can either (a) make a copy of the Google sheet or (b) download it as an Excel file from the File menu so that you can edit and work on it:

>> Estimated base-oil viscosity @ 150 °C (BO DV150) and VII content of selected oils <<

Input values needed (gold columns):

  • oil name (info only)
  • density at 60 °F (15.6 °C) (g/cm³)
  • KV40 (cSt)
  • KV100 (cSt)
  • VI (info only)
  • HTHS (cP) (high-temperature, high-shear viscosity)


Output calculated (green columns):

  • A_Harman index: a measure of the effective viscosity-index improver (VII) content through the temporary shear of the oil
  • VII content: effective VII content (measured by the temporary shear, not the actual solid or oil-solvent-dissolved VII content) directly given by the A_Harman index
  • BO DV150 (HTFS) (cP): base-oil (plus the additive package) viscosity at 150 °C excluding the VII -- high-temperature, full-shear viscosity -- directly given by the A_Harman index and HTHS


The most remarkable output of the calculator is the base-oil viscosity (full-shear viscosity) at 150 °C (BO DV150 = HTFS), which applies to the valvetrain, timing-chain, piston-ring, and cylinder-liner wear since the oil goes through full shear in these engine components, whereas the HTHS (high-shear viscosity) applies to the bearing wear since the oil goes through high shear but not full shear in the bearings.

Important notes: The base-oil viscosity includes both the base oil and detergent - dispersant - inhibitor (DDI) package. Some base oils, such as POE base stocks and high-viscosity PAO base stocks, temporarily shear like a VII and may appear as an effective VII content in the calculation.

Note that I have also improved the accuracy of the calculator by accounting for the ASTM D341 underestimation of KV150 using a slightly higher density correction factor (0.917) when calculating DV150.

You can read the theory and discussion in the thread below. I have recently verified the accuracy of the base-oil-viscosity calculator against the test oils in the Hugh Spikes paper, which can be found at the end of this theory thread:

HTFS: high-temperature, full-shear viscosity

[Linked Image from lh3.googleusercontent.com]


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Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423656 05/07/20 08:34 PM
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ZeeOSix Offline
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Gokhan - I know you've posted a lot of info in the past about all of this, but in your eyes what are the key output parameters to look at, and why when choosing an oil?

We all know that higher HTHS is typically better for engine protection, but what other parameters in your data matrix could be used to rate oils from 1 to x?

Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423680 05/07/20 09:02 PM
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Thanks for all the work.

Last edited by DrDanger; 05/07/20 09:08 PM.
Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423688 05/07/20 09:11 PM
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Gokhan you really are something...

Extremely intelligent and always thinking about very complicated concepts...

My hats off to you... I appreciate your hard work and thought processes... Very impressive smile


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Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: ZeeOSix] #5423690 05/07/20 09:14 PM
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Gokhan Offline OP
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Originally Posted by ZeeOSix
Gokhan - I know you've posted a lot of info in the past about all of this, but in your eyes what are the key output parameters to look at, and why when choosing an oil?

We all know that higher HTHS is typically better for engine protection, but what other parameters in your data matrix could be used to rate oils from 1 to x?

I use the table for information rather than rating oils.

That said, for better wear protection, I would look for an oil with a higher high-temperature, full-shear viscosity (HTFS, not HTHS), which is labeled as BO DV150 (= HTFS) in my table, BO meaning base oil. That's because HTHS is usually fixed by the oil spec or oil type and the variation in insignificant -- 2.6 - 2.7 cP for a 0W-20 and 3.0 - 3.2 cP for an ILSAC 5W-30 -- but HTFS can vary greatly. For most people HTFS will make a bigger impact on wear than HTHS because HTFS has a direct effect on wear vs. HTHS acting more like an insurance against wear. Of course, HTFS and HTHS are directly related to each other through the A_Harman index; however, as I said HTFS varies a lot more than HTHS for a given oil spec or oil type as the A_Harman index varies, and you can use the table to find an oil with a significantly higher HTFS for a given oil spec or oil type.

For engine-deposits control, a smaller VII content (= a larger A_Harman index) will help.


2020 Toyota Prius Prime XLE plug-in hybrid, 2ZR-FXE engine, ~ 65 mpg on regular gasoline, ~ 5,000 mi
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Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: bbhero] #5423693 05/07/20 09:17 PM
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Gokhan Offline OP
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Originally Posted by bbhero
Gokhan you really are something...

Extremely intelligent and always thinking about very complicated concepts...

My hats off to you... I appreciate your hard work and thought processes... Very impressive smile

Thank you for your kind words, bbhero!


2020 Toyota Prius Prime XLE plug-in hybrid, 2ZR-FXE engine, ~ 65 mpg on regular gasoline, ~ 5,000 mi
TGMO 0W-16 SN/RC Japan
OEM spin-on oil filter Japan
Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423694 05/07/20 09:25 PM
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No problem... Just saying it the way it is...

And in your case... Your awesome... And gifted..


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"Treat your family like your friends and treat your friends like your family."
Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423697 05/07/20 09:27 PM
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thumbsup

Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423732 05/07/20 11:05 PM
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Originally Posted by Gokhan
Originally Posted by ZeeOSix
Gokhan - I know you've posted a lot of info in the past about all of this, but in your eyes what are the key output parameters to look at, and why when choosing an oil?

We all know that higher HTHS is typically better for engine protection, but what other parameters in your data matrix could be used to rate oils from 1 to x?

I use the table for information rather than rating oils.

That said, for better wear protection, I would look for an oil with a higher high-temperature, full-shear viscosity (HTFS, not HTHS), which is labeled as BO DV150 (= HTFS) in my table, BO meaning base oil. That's because HTHS is usually fixed by the oil spec or oil type and the variation in insignificant -- 2.6 - 2.7 cP for a 0W-20 and 3.0 - 3.2 cP for an ILSAC 5W-30 -- but HTFS can vary greatly. For most people HTFS will make a bigger impact on wear than HTHS because HTFS has a direct effect on wear vs. HTHS acting more like an insurance against wear. Of course, HTFS and HTHS are directly related to each other through the A_Harman index; however, as I said HTFS varies a lot more than HTHS for a given oil spec or oil type as the A_Harman index varies, and you can use the table to find an oil with a significantly higher HTFS for a given oil spec or oil type.

For engine-deposits control, a smaller VII content (= a larger A_Harman index) will help.


Thanks for the explanation and all the hard work you've done with all this data crunching.

Looks like the 5W-30 oil I'm using has a pretty high BO DV150 value compared to other 5W-30 in your table. It also has a relatively small VII content and low Noack (from manufacturer's spec sheet). Guess I like it even more now ... grin2

Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423773 05/08/20 02:37 AM
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Gokhan,

I may have asked you this question before but can't recall.
Did A_Harman publish his equation or just the values?

are you calculating A_Harman index based on your equations or his published equations and how close are the values?

Btw I like your data and use your .xlsx as a reference and for relative comparison and my question is just out of curiosity ...

Also what would be the outputs for a theoretical "pefect" oil?
A_Harman: 1.0
VII: I assume 0
BO DV150: ? What's the perfect value here? 4.0? Infinity?


Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: OilUzer] #5423778 05/08/20 03:24 AM
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Originally Posted by OilUzer
Gokhan,

I may have asked you this question before but can't recall.
Did A_Harman publish his equation or just the values?

are you calculating A_Harman index based on your equations or his published equations and how close are the values?

Btw I like your data and use your .xlsx as a reference and for relative comparison and my question is just out of curiosity ...

Also what would be the outputs for a theoretical "pefect" oil?
A_Harman: 1.0
VII: I assume 0
BO DV150: ? What's the perfect value here? 4.0?

Yes, it is basically the same A_Harman index as the original one by A_Harman, the only difference being that I use 0.917 for the density correction factor (to extrapolate the density from 15.6 °C to 150 °C) in my latest version. This improves the accuracy by making up for the systematic underestimation of KV150 by the ASTM D341 extrapolation for oils containing a VII. A_Harman himself had used 0.885, which is on the low side and doesn't take into account the systematic underestimation by ASTM D341 I mentioned.

A_Harman index = HTHS150 / (density150 × KV150) = HTHS150 / (density15.6 × density correction factor × KV150)

To answer your question, an ideal monograde oil (it's fine if you want call it perfect) would have:

  • A_Harman index = 1
  • effective VII content = 0%
  • BO DV150 (HTFS150) = HTHS150 (the base-oil (full-shear) viscosity is the same as the high-shear viscosity)


However, even neat base stocks -- in other words base stocks that aren't mixed with a VII -- temporarily shear to some extent, especially POE and high-viscosity PAO base stocks. Therefore, even if you have a monograde oil, A_Harman index may be smaller than 1, and the temporary shear of the base stocks may appear as the presence of a VII, even if there isn't one. Therefore, it is important to keep in mind that both the A_Harman index and effective VII content measure the temporary shear and not necessarily an actual VII content by weight or volume. Note that if, say, A_Harman index = 0.98 = 98%, then the effective VII content = (100% - 98%) / 2 = 1%, which may be right on the money for certain commercial VII types (like the ExxonMobil blend-guide oils in my table), but this is somewhat arbitrary as a manufacturer can sell even the same VII in different concentrations dissolved in a different amount of an oil solvent. So, keep in mind that it is an effective VII content directly corresponding to the amount of the temporary shear, which is what the A_Harman index measures.


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Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423825 05/08/20 06:36 AM
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The law of parsimony is not at work here.

Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423944 05/08/20 09:15 AM
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Great work Gokhan! thumbsup


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Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423969 05/08/20 09:55 AM
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Awesome work, Gokhan. Thanks for sharing it. Gonna take me some time to digest it all.


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Re: Automated calculator for the A_Harman index, VII content, and base-oil viscosity [Re: Gokhan] #5423974 05/08/20 10:04 AM
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I know it will be kind of comparing apples to oranges but it would be interesting to combine the 3 output columns (using a tbd formula) and come up with a relative ranking column.
Rank = 1..n
n = number of oils

Even though the formula will for example be ranking a 5W30 against a 0W20 (apples to oranges) they are all in the same boat so the final ranking of two different 5W30's will be relative to the the best oil (rank #1). That way one can quickly determine which 5W30 got a better grade than the other bsed on your analysis.

We also have to be aware of the fact that if you are dealing with 100 near perfect oils, some will rank lower and that doesn't mean they are bad.

However, the negative thing about the ranking column would be additional heated discussions like there is no way oil x is better than oil y ... lol



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