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Re: Help a not-so-noob: shear stability theory. [Re: benjy] #5292517 12/12/19 01:58 PM
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Originally Posted by benjy
as noted there are many UNKNOWN variables in todays lubricants that only the BLENDER or a pro like MOLA understands if given complete specs. on machinery lubrication there was a graph showing how much faster a group III + lower thickens in the cold as well as they thin more in the heat. remember cold aka winter specs are at 40C aka 104F from there all is downhill. real synthetic PAO + Ester oils are totally pure with NO wax present but lesser oils refined from CRUDE have some or some more depending on the group. average joe will NEVER know + understand all there is to know about lubricants!! looking at Redline Ester lubes shows that lighter blends have less durability than slightly thicker ones even thou base oils are some of the best!! everything today is made to a price point so don't expect the best from cheaper lubricants IMO, thou lubes have surely improved even for a mid priced fake synthetic!!


Huh? sounds like a broken record with an out of date talking point that was lost a few years ago.


2018 Trd Pro 4Runner
2018 Tacoma off-road

Dealer 0w20 to M1 0w40 FS -it depends
Re: Help a not-so-noob: shear stability theory. [Re: OilStasher] #5292572 12/12/19 03:04 PM
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From what I've read, the viscosity improvers are what do most of the shearing, and they've improved since the old days, when 10W40 turned into rubbery sludge in your crankcase if used too long. Amsoil (& possibly others) make a full synthetic SAE 30 that has good enough flow characteristics to be a 15W without VIIs-an oil like that would be the most shear stable of all. That was the reasoning behind Delo 400 SD 15W30-the smaller viscosity spread compared to 15W40 would (in theory) make it a better stop/start HDEO.


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Re: Help a not-so-noob: shear stability theory. [Re: bullwinkle] #5292576 12/12/19 03:09 PM
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RDY4WAR Offline
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Originally Posted by bullwinkle
From what I've read, the viscosity improvers are what do most of the shearing, and they've improved since the old days, when 10W40 turned into rubbery sludge in your crankcase if used too long. Amsoil (& possibly others) make a full synthetic SAE 30 that has good enough flow characteristics to be a 15W without VIIs-an oil like that would be the most shear stable of all. That was the reasoning behind Delo 400 SD 15W30-the smaller viscosity spread compared to 15W40 would (in theory) make it a better stop/start HDEO.


Many PAO synthetics can pass SAE J300 requirements for a 10w-30 without VII and some can pass for 5w-30. Instead of using VII, you use something like mPAO which has a KV100 of 65 cSt (or 100 or 120 cSt) but a VI of 179 and pour point of -44*C. Of course this is exponentially more expensive than group III + VII.

Last edited by RDY4WAR; 12/12/19 03:09 PM.

"He who is without oil, shall throw the first rod." - Compressions 9:1
Re: Help a not-so-noob: shear stability theory. [Re: DrDanger] #5292626 12/12/19 04:07 PM
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Mad_Hatter Offline
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Originally Posted by DrDanger

Do you have a link to some general info on SSI of VM's? I (and many here I guess ) would very much appreciate that.

Google shear stability index and you'll find info about it. Check out the additive mfg sites like Lubrizol, Infineum and Oronite...but be careful, it's another time sucking rabbit hole filled with stuff like thickenning efficiency (TE), SSI, polymers etc..😂 (meaning, very dry reading but information none the less)

Last edited by Mad_Hatter; 12/12/19 04:08 PM.
Re: Help a not-so-noob: shear stability theory. [Re: RDY4WAR] #5292636 12/12/19 04:14 PM
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Originally Posted by RDY4WAR

Many PAO synthetics can pass SAE J300 requirements for a 10w-30 without VII and some can pass for 5w-30. Instead of using VII, you use something like mPAO which has a KV100 of 65 cSt (or 100 or 120 cSt) but a VI of 179 and pour point of -44*C. Of course this is exponentially more expensive than group III + VII.

Lifted from Infineum fwiw...

[Linked Image]

Re: Help a not-so-noob: shear stability theory. [Re: OilStasher] #5292651 12/12/19 04:29 PM
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Impatient Offline
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Soooo...

1) using 5w30 as the example, people argue over whether KV100 10cst is better or worse than 9cst (or 9.2 is better than 8.2 in a UOA). KV40 specs are sometimes on PDS’s, but we rarely see them on VOA’s or UOA’s, but in general, to continue with 5w30 example, are generally between upper 50’s to 70 (a numerically wider spread than 8 to 9, or even 10). We never see 0C KV spec’s do we? Seems 0C would be a useful number, more relevant than -40C specs, except for those poor souls who have to start their engines in N. Dakota winter. But look at how big those visc numbers are at pour point. Us newb-mere-mortals can’t even comprehend the difference in the typical numbers. As pointed out above, some 0w30’s are “thicker in the middle” than 5w30’s, though don’t hit the wall at sub-sub-sub freezing Arctic temperatures. It would be nice to know oil specs for 0C, then some some mid-point (and I dont have a problem with 40C), then the “normal” engine temp of 100C. And I don’t mean we should take away the readings useful to the Dakotans.

2) taking it the other direction, I’ve read arguments over HTHS readings of 3.5 or “better” vs 3.1 or “worse.” Numerically, a small difference. But seems safe to say, when the “normal engine temp” is 100C, the oil temp in a turbo, or even a main bearing, might be significantly higher. So the closest surrogate I’ve seen is the HTHS number, but really, how much better is 3.5 compared to 3.1, or 2.9? What delta is really considered significant here?

3) obviously, synthetic vs conventional designation has been smeared so badly, only a handful can make sense of the outlandish performance claims. Thanks to the poster above for explaining how grIV might need less VI treatment than a grpIII, and I guess that was meant to say the grpiV would shear less. But not all synthetics are grpIV.🙁

4) I get the sense, a fair number of people think “modern” oils are less protective than certain older specs (and I don’t mean 1970’s specs, but say, recent 10w30, 0w40 or 5w40 vs “government-mandated” or government-encouraged 0w20’s. Conversely, some equate SN+ to nirvana.

Someone comment on how a newb-mere-mortal, such as myself, can differentiate oil quality. And the first person who says, “just use what’s in the owners manual,” gets the sit-down-and-shut-up buzzer, because that helps no one understand. I love clean air, and non-polluted environments, but for the moment, can we take fuel-economy out of the discussion, and focus on wear protection? Well, it’s OK to discuss deposits, varnish, and sludge.

For the record, both my vehicles have turbos, and lots of rants about how hard they are on oil (especially the Subaru). But you can find my Ford UOA’s, and I don’t remember anyone saying, “Gee that ILSAC GF5 GrpIII+ Synthetic sure did great.” So I tried the Valvoline PBRestore, and people DID say “gee, that oil did great” but I have no intention of making that my regular fill. Can’t afford that, although cheaper than an engine tear down. So still searching for the affordable unicorn oil.

Last edited by Impatient; 12/12/19 04:40 PM.

15 Ford Transit 250 3.5EB Turbo
07 Subaru OBXT 2.5 Turbo Castrol Euro 0w30
Re: Help a not-so-noob: shear stability theory. [Re: OilStasher] #5292686 12/12/19 05:01 PM
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It probably helps to mention the scope of my comments. When most people here mention engine oil as a broad term, they're usually referring to the oils they can easily find on the shelf at Autozone. Those oils only make up about half of my "spectrum" that I base my comments on. The other half includes Amsoil, Red Line, Driven, Schaeffer's, High Performance Lubricants, LAT, and so on. It's correct that PAO is sparingly used in the "common" oils.

The common API oils are all within a very small box with only minute differences from brand to brand.

Last edited by RDY4WAR; 12/12/19 05:03 PM.

"He who is without oil, shall throw the first rod." - Compressions 9:1
Re: Help a not-so-noob: shear stability theory. [Re: OilStasher] #5293063 12/13/19 02:26 AM
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According to most auto manufacturers , the oil selection doesn't matter. we have 3 cars that the owner's manual specifies 5W30 or 10W30 and change the oil for example every 7500 miles ... no mention of the oil type (dino, blend ,syn).

Can you expect the same performance using a cheaper dino vs. a good syn after 100K miles? Evidently auto manufacturers do at least for many average cars ...

Re: Help a not-so-noob: shear stability theory. [Re: OilUzer] #5293077 12/13/19 03:28 AM
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RDY4WAR Offline
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Originally Posted by OilUzer
According to most auto manufacturers , the oil selection doesn't matter. we have 3 cars that the owner's manual specifies 5W30 or 10W30 and change the oil for example every 7500 miles ... no mention of the oil type (dino, blend ,syn).

Can you expect the same performance using a cheaper dino vs. a good syn after 100K miles? Evidently auto manufacturers do at least for many average cars ...


The act of performing maintenance is far more important than the type or brand of oil chosen. The type and brand comes down to wanting a longer than 7500 interval or wanting less friction for better fuel economy or wanting the lowest SAPS possible, etc...

The big question for the auto manufacturers is what will ensure the engine will run well for the life of the warranty or 100k miles? Usually once you've passed that mark, they're more interested in selling you a new car than keeping the old one running. Not saying the OEM recommendations can't keep a car alive for 500k+ miles as it certainly can and does in some cases.


"He who is without oil, shall throw the first rod." - Compressions 9:1
Re: Help a not-so-noob: shear stability theory. [Re: OVERKILL] #5295541 12/15/19 11:23 PM
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Originally Posted by OVERKILL
Yeah, you are completely lost. Let me try and make this a bit clearer:

The Winter rating of an oil is simply the oil's ability to pass the CCS and MRV requirements at a given set of temperatures. It has no formal applicable viscosity figure associated with it, just a loose set of limits defined by the SAE. So whether it's a 0w-8 or a 0w-50, all that means is that it was able to pass CCS and MRV at -35C and -40C respectively.

ALL oils thicken as they cool. Some 0w-xx's may actually thicken MORE than their 5w-xx counterparts, but will not have the viscosity "wall" that occurs when the waxes in the base oil crystallize, driving up viscosity dramatically and causing it to fail meeting the CCS and MRV requirements for 0w-xx.

GENERALLY, the narrower the spread between the Winter rating and the 100C visc, the less VII polymer used in the oil. This is because you need a lighter base oil to meet the lower Winter ratings. This base oil is then "pumped up" with VII to meet the 100C target. HOWEVER, there are exceptions. A lubricant using a PAO base can get away with a heavier base blend and less VII than one using your run of the mill Group III or especially Group II. So if all things were equal (same base used) then the rule holds true, however that's often not the case. XOM for example uses significantly more PAO in many of their 0w-xx products, some being almost entirely PAO-based like their EP and AP 0w-20's, so in this case, these oils, despite the spread, may actually have LESS VII than some cheaper based 5w-20's.

Does that make sense?
Sorry for the delay. I didn't post and bail! So I'm still a bit confused, why is it that a lower rating spread (which thins more with heat) is more shear stable? I've reread this post probably ten times, and I don't get it. Is my correlation between thickening/thinning and shear stability just completely wrong? Are they just completely unrelated? shrug

I'm genuinely trying to learn, and I feel like the "kid left behind." LOL


Sludge-Ushering, Problematic, Economically-Retarded, Toxic, Egregious, Certifiably Horrible. Just like the company that sells it. cool
Re: Help a not-so-noob: shear stability theory. [Re: OilStasher] #5295559 12/16/19 12:03 AM
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CR94 Offline
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Originally Posted by OilStasher
... why is it that a lower rating spread (which thins more with heat) is more shear stable? I've reread this post probably ten times, and I don't get it. Is my correlation between thickening/thinning and shear stability just completely wrong? Are they just completely unrelated? ...
Because, other things being reasonably equal, the low-spread version is less dependent on VI additives to maintain its hot viscosity, and those additives (some of them, anyway) are susceptible to shear damage. That doesn't mean a 5W-30, for example will shear until it's thinner than a 5W-20 of the same brand and line, but means that it might lose a greater percentage of its (higher) original hot viscosity. Thus, the 5W-20 would be more stable.


2011 Toyota Prius now at 107K
1981 Mazda GLC (323) retired at 606K
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Re: Help a not-so-noob: shear stability theory. [Re: CR94] #5295709 12/16/19 07:30 AM
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Originally Posted by CR94
Originally Posted by OilStasher
... why is it that a lower rating spread (which thins more with heat) is more shear stable? I've reread this post probably ten times, and I don't get it. Is my correlation between thickening/thinning and shear stability just completely wrong? Are they just completely unrelated? ...
Because, other things being reasonably equal, the low-spread version is less dependent on VI additives to maintain its hot viscosity, and those additives (some of them, anyway) are susceptible to shear damage. That doesn't mean a 5W-30, for example will shear until it's thinner than a 5W-20 of the same brand and line, but means that it might lose a greater percentage of its (higher) original hot viscosity. Thus, the 5W-20 would be more stable.


Yes, exactly. And its not always the case either, it's just a rough guideline, as base oil selection can play into this.


2019 RAM 1500 Sport - Mobil 1 EP 0w-20, FRAM Ultra
2020 Grand Cherokee SRT - Ravenol SSL 0w-40, FRAM Ultra
Re: Help a not-so-noob: shear stability theory. [Re: OilStasher] #5295721 12/16/19 07:48 AM
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Shearing in passenger car motor oils has to be on of the most overrated issues on this board. First of all, nearly all the UOA here are from Blackstone who have been shown to not be able to discriminate between mechanical shear and fuel dilution, let alone properly measure viscosity in the first place. So even if you believe that a tested oil has deviated from the initial viscosity there's no way to tell why that happened.

Moreover not all viscosity index improvers are equal. That has been discussed many times, some are more shear resistant than others. So blanket statements about multi-viscosity oils does not apply without knowing specifics about the oil under question. In addition the oil molecules themselves (regardless of the Group designation) do not shear as they are far too small to do so. So from that standpoint that's irrelevant.

And lastly, the propensity for mechanical shear is highly application dependent. Some engines are more prone to shearing the VII due to their internal design (such as gear-driven camshafts).

For the most part there is precious little evidence that actual mechanical shear is anything to worry about for the vast majority of engines and oils on the market.


1994 BMW 530i, 251K
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Re: Help a not-so-noob: shear stability theory. [Re: CR94] #5295736 12/16/19 08:04 AM
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Originally Posted by CR94
Because, other things being reasonably equal, the low-spread version is less dependent on VI additives to maintain its hot viscosity, and those additives (some of them, anyway) are susceptible to shear damage. That doesn't mean a 5W-30, for example will shear until it's thinner than a 5W-20 of the same brand and line, but means that it might lose a greater percentage of its (higher) original hot viscosity. Thus, the 5W-20 would be more stable.

Ah, this makes a little more sense. So it's not the oil that shears, it's the additives? Hmm. Maybe that's solved. But I think I'm still lost on the "low-spread" (example 5W-20) actually being less of a "spread" than 'high-spread' (example 0W-40). There is less thinning with 0W-40 than 5W-20. Meaning 0W-40 starts moderately thin and doesn't thin much when heated. 5W-20 starts slightly thick and thins a substantial degree down to a 20. Why is 5W-20 less of a spread? That sounds completely backwards to me.

It's amazing. The things I've "known" for years suddenly get questioned and I flip my own world upside-down with technicalities. Haha.


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Re: Help a not-so-noob: shear stability theory. [Re: OilStasher] #5295751 12/16/19 08:24 AM
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kschachn Offline
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Originally Posted by OilStasher
But I think I'm still lost on the "low-spread" (example 5W-20) actually being less of a "spread" than 'high-spread' (example 0W-40). There is less thinning with 0W-40 than 5W-20. Meaning 0W-40 starts moderately thin and doesn't thin much when heated. 5W-20 starts slightly thick and thins a substantial degree down to a 20. Why is 5W-20 less of a spread? That sounds completely backwards to me.

That makes no sense, what are you trying to ask? All oils regardless of grade are very thick when cold and much thinner when hot. No oil goes in the opposite direction.


1994 BMW 530i, 251K
1996 Honda Accord, 280K
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