High VI and Base Stocks

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With all the hoopla about high VI being the holy grail of engine oils i found this interesting.
When one poster claims TGMO to be the best because it has higher VI than say Mobil 1 or PP/PU it seems he may be ignoring the effects of the base stock.

Quote:
Viscosity Index/Improver Additives

Viscosity Index (VI) is the term used to rate a base oil or an oil products ability to resist thickening and thinning with temperature change. These VI improvers are typically thin straight polymers, or polymers that “unwind” and straighten out at higher temperatures. This helps to maintain a more consistent viscosity of a wider range of temperatures. But, typical VI improving additives are far more fragile than the base oil and are easily sheared in half under a variety of operating conditions. HD diesel applications use VI improvers that are more durable. And, higher grade base stocks have less need for VI improvers. Some top tier synthetic oil products meet SAE 5W-30 ratings without any VI improvers.


http://www.diagnosticnews.com/oil-additives-supplements/
 
Originally Posted By: Trav
I didn't see mention of VII just VI.

You didn't see the words "VI improvers" in the text you quoted?
smile.gif
 
Originally Posted By: Oil Changer
I'd like to know which of those 5W-30s have no VII.


Redline 5w-30 for one.
 
Might be why AFE has a less than impressive V index, yet great cold flow specs.
 
Originally Posted By: webfors
Might be why AFE has a less than impressive V index, yet great cold flow specs.


Likely. And same goes for the EP 0w-20 with its big slug of PAO in it IMHO.
 
Originally Posted By: Quattro Pete
Originally Posted By: Trav
I didn't see mention of VII just VI.

You didn't see the words "VI improvers" in the text you quoted?
smile.gif




Yep i see it now. Don't get exited, i lose somethings in translation.
 
I think higher VI with minimum or no VII is better than one with high VII. As mentioned by OVERKILL, M1 0w20 EP is a good 20 weight oil with higher PAO contain than other M1 weight. Especially when Walmart had it for $21-22 5-qt jug some months ago.
 
Yeah says PAOs don't have wax. Group III do and that's why you use PPD

No oil can be a multi grade without a VII. Otherwise it's just a monograde.

Any finished oil with s VI over the VI of the base oil will have VII
 
Originally Posted By: bobbydavro
Yeah says PAOs don't have wax. Group III do and that's why you use PPD

No oil can be a multi grade without a VII. Otherwise it's just a monograde.

Any finished oil with s VI over the VI of the base oil will have VII


Sure it can, if it satisfies the requirements for both 5W and SAE 30, then it can be labelled as an SAE 30 straight grade, or a 5w-30.

AMSOIL has a 10w-30 that is an SAE 30 for the same reason: No VII's. This is the same as Redline's 5w-30.

It isn't overly common, but these products do exist.
 
Timely thread Trav, as I've been piecing together some cogent arguments for 3-4 days to start a thread, will throw them in here.

KrisZ has an interesting opener for this little chart from Conoco Phillips.

brookfield.jpg


Quote:
PAOs have inherently high viscosity indexes (VI) while maintaining excellent low-temperature performance. Both properties are critical in protecting engines at temperature extremes. Low temperatures can rob a lubricant of its ability to reach critical parts, while high temperatures can thin and break down an oil, crippling its lubricating ability.

However, two different lubricants with the same viscosity index may perform dramatically differently at low temperatures. Other factors shown on the chart below need to be considered.


Note, two basestocks, same KV40 and KV100, and thus the same dimensionless number for VI of 140...and they behave markedly different when they get cold...the PAO meets 0W, the GrIII probably 10W, requiring additive intervention.

Takeaway for me is that VI shouldn't be used to decide what's good (actually, I DO use VI, anything with a stratospheric VII without a good reason (e.g. basestock), I avoid like the plague).
 
Looking at the Afton additive treat charts for their HiTech 5710 Polymethacrylate VII/dispersant.

Afton%20VII%20treat%20rate.jpg


Looks like there's a number of ways to make a 30 grade oil according to the chart (note there's no HTHS, so the first may well not be a 30)

3cst base oil and 10% 5710 polymer, KV100 10.84, VI 262 - almost certainly a 0W.
4.1cst base oil, (about) 7-8% 5710, and a VI over 200 - again almost certainly a 0W
5cst base oil, 5% polymer, KV100 10.07, VI 176. Probably still a 0W.

Again reinforces my view that I avoid unicorn type VIs, as the last of the recipes will be naturally less volatile, more shear stable, and likely retain it's viscosity, less thickening or thinning better through the OCI.
 
Originally Posted By: OVERKILL
Originally Posted By: bobbydavro
Yeah says PAOs don't have wax. Group III do and that's why you use PPD

No oil can be a multi grade without a VII. Otherwise it's just a monograde.

Any finished oil with s VI over the VI of the base oil will have VII


Sure it can, if it satisfies the requirements for both 5W and SAE 30, then it can be labelled as an SAE 30 straight grade, or a 5w-30.

AMSOIL has a 10w-30 that is an SAE 30 for the same reason: No VII's. This is the same as Redline's 5w-30.

It isn't overly common, but these products do exist.


True that....

I've been playing a lot with A_Harman's technique for comparing the high shear and theoretical newtonian behaviours of lubricants.

Basically, use the KV40 and KV100 into the widman operational viscosity calculator, and calculate for 150C...multiply by density, and 0.885.

That will be the "KV150". Divide the HTHS by teh KV150 to get the "stability" as a ratio.

In a Newtonian (non VIIed) fluid the KV150 and HTHS should be the same number, so the ratio should be 1.

Some examples
Edge 25W50, KV40 204, KV100 21, density 0.8883, HTHS 6.1, Harman Index 1.06.
Amsoil ACD, KV40 69.0, KV100 10.6, density 8.539, HTHS 3.4, Harman Index 1.02.

So both of those oils are probably "straight" grades, with little to no VII added...the latter must have no VII for Amsoil to be able to rate it as a mono.

TGMO, KV40 36.1, KV100 10.6, density 0.851, HTHS 2.6 (for a little while), Harman Index 0.844.

Indicates lots of propping up through VIIs.

Couple of others
M1 0W40, KV40 75, KV100 13.5, density 0.85, HTHS 3.8, Harman Index0.874.
Magnatec 5W30, KV40 66, KV100 10.9, density 0.8595, HTHS 3.2, Harman Index 0.915

My new and current favourite oil
Edge 5W30 A3/B4, KV40 71.8, KV100 12, Density 0.8533, HTHS 3.6, Harman Index 0.946

(Redline 5W30 calculates out at 0.917, but they only list one density for all grades, so bad numbers in makes it not worth the effort)
 
So AFE 0w-30:

KV100: 10.9
KV40: 62.9
Density: 0.842
HTHS: 3.0
KV150: 3.47

Harman Index: 0.865


AFE 0w-20:
KV100: 8.7
KV40: 45.8
Density: 0.841
HTHS: 2.7
KV150: 2.89

Harman Index: 0.934 (boy, that's a lot better than TGMO! LOL!)
 
OVERKILL, that's a good comparison too...look at the densities, and you can (almost) say that the difference between the two is VII.
 
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