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#3211391 - 12/09/13 03:10 PM Curious about VI and MRV
Jeffs2006EvoIX Offline


Registered: 02/28/10
Posts: 1287
Loc: Imperial Valley, California
Was just curious of the importance of VI vs MRV values.

Oil as an example. M1 0w40. VI = 185 which is all thumbs up vs. a MRV of 31,000 which is not

I was under the impression that an oil with a High VI meant for a good "All Climate" oil, but with a MRV of 31,000 how can that be?

Can anyway clarify the importance of each?

Granted I live in Southern California and where I live the coldest it gets is around 25F in the winter, but still, just out of curiosity.

Thanks

Jeff
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#3211397 - 12/09/13 03:15 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
NateDN10 Offline


Registered: 01/10/10
Posts: 1390
Loc: Rochester, NY
MRV is related to extreme cold (for example, measured at -40).
VI is related only to the +40C and +100C viscosity.
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#3211401 - 12/09/13 03:18 PM Re: Curious about VI and MRV [Re: NateDN10]
Jeffs2006EvoIX Offline


Registered: 02/28/10
Posts: 1287
Loc: Imperial Valley, California
it just puzzles me because 40C is around 104F and 100C is around 212F. So is MRV is better number to be looking at for Cold Start Protection?

I think M1 0w40 is around 75 at 40C so how is it at lets say 32F? Vs. an oil with a better MRV? Just curious as to the point of wear at cold start up.

Jeff
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#3211408 - 12/09/13 03:23 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
NateDN10 Offline


Registered: 01/10/10
Posts: 1390
Loc: Rochester, NY
IMO, there's a lapse in the specs right where most people would care about it: 0F to 32F.

I'm not the most knowledgeable, but I believe I've read that MRV and CCS numbers are more indicative of cold-start behavior than viscosity at 40C.
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#3211409 - 12/09/13 03:23 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
CATERHAM Offline


Registered: 11/18/05
Posts: 9448
Loc: Burlington, Ontario, Canada
Jeff, in your climate MRV has no relevance.

-For a given oil grade a higher VI oil will be lighter on start-up and during warm-up than a lower VI oil.
-At normal operating temp's, if two oils have the same operational viscosity, the oil with the higher VI will have a higher HTHSV rating as well.
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#3211416 - 12/09/13 03:29 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
Tucson Five-O Offline


Registered: 05/29/06
Posts: 222
Loc: Tucson, AZ
Jeffs2006EvoIX,

VI is simply the calculation from the 40CKV and 100CKV readings. My personal belief is that many modern synthetics have complex base oil interactions that VI alone cannot predict what MRV values will be. Pennzoil Ultra which does not have impressive VI values, has very good MRV values. Posters here that work in the industry, such as salv and solarent would certainly be able to expound on why. Even the Mobil 1 AFE series has somewhat unimpressive VI (166 for 5W-30), but class leading MRV (-40C) values.

My guess is, compared to the SM Mobil 1 OW-40, there is a lower percentage of PAO, and more Group III+ base oil, such as XOM Visom, hence the higher MRV published value.

The one area that PAO still wins out over Group III+ base oils, hands down, is MRV and CCS values.

But, as most knowledgeable posters continually (and correctly IMHO) reiterate, the total package, base oils and additives are "where it's at". XOM, after their Katrina hiccup, have worked hard to get their Group III+ oils, which in fairness, most likely, per knowledgeable sources, still have an unknown % of PAO, to be an overall excellent value, both from an engine wear protection/cleanliness versus longevity standpoint.

If you need OW-40 for your applications, which if memory serves me correctly, lean towards racing and modified, then again IMHO, you simply cannot do better than Mobil 1. An extremely high technology cutting edge robust oil, it is.

Gary
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2013 Summit White Chevrolet Cruze Eco 6AT 21000 miles Mobil 1 5W-30/OEM (ACDelco/Hengst)

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#3211424 - 12/09/13 03:36 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
CATERHAM Offline


Registered: 11/18/05
Posts: 9448
Loc: Burlington, Ontario, Canada
Originally Posted By: Jeffs2006EvoIX

I think M1 0w40 is around 75 at 40C so how is it at lets say 32F? Vs. an oil with a better MRV? Just curious as to the point of wear at cold start up.Jeff

Yes M1 0W-40 has a KV40 of 75cSt. If you plug the KV40 and KV100 spec's into a viscosity calculator you'll can approximate the kinematic viscosity at 0C (32F) which would be 563cSt:

http://www.widman.biz/English/Calculators/Graph.html

Of course a 0W/5W-30 will have a lower viscosity at 32F even with a lower VI. For example M1 5W-30 with it's 172 VI will have a viscosity at 32F of 490cSt.
So all things being equal, a 5W-30 will provide less start-up wear than M1 0W-40 and an even lower VI 5W-20 will offer even less start-up wear.
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94 Caterham 7 Sustina 0W-20 80%/0W-50

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#3211425 - 12/09/13 03:38 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
Jeffs2006EvoIX Offline


Registered: 02/28/10
Posts: 1287
Loc: Imperial Valley, California
Thanks Guys for your replies. Just curious on VI vs MRV at cold start. Common sense would tell you the lower the MRV the better cold start flow would be? Right? Meaning, you shouldnt need to be in -50F weather to obtain the benefits of a good MRV oil.

I am happy with the M1 0w40 that I am using. I just was curious is the VI value more important vs MRV.

As stated by Gary PU 5w40 Euro does have less VI but a better MRV, so in all practicality does that mean anything?

Is having a higher VI more importnat than a lower MRV?

Jeff
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#3211428 - 12/09/13 03:41 PM Re: Curious about VI and MRV [Re: CATERHAM]
Jeffs2006EvoIX Offline


Registered: 02/28/10
Posts: 1287
Loc: Imperial Valley, California
Originally Posted By: CATERHAM
Originally Posted By: Jeffs2006EvoIX

I think M1 0w40 is around 75 at 40C so how is it at lets say 32F? Vs. an oil with a better MRV? Just curious as to the point of wear at cold start up.Jeff

Yes M1 0W-40 has a KV40 of 75cSt. If you plug the KV40 and KV100 spec's into a viscosity calculator you'll can approximate the kinematic viscosity at 0C (32F) which would be 563cSt:

http://www.widman.biz/English/Calculators/Graph.html

Of course a 0W/5W-30 will have a lower viscosity at 32F even with a lower VI. For example M1 5W-30 with it's 172 VI will have a viscosity at 32F of 490cSt.
So all things being equal, a 5W-30 will provide less start-up wear than M1 0W-40 and an even lower VI 5W-20 will offer even less start-up wear.


Thanks CATERHAM for the info. My application calls for a VW 502 approved oil so I cant use just any 5w30. Most oils in that grade are heavy 30w's like GC.

Just seems to me, that "If" most wear of an engine does indeed occur at start up, wouldnt a lower MRV play a role in reducing wear even in warmer climates?

Not trying to think too much on it, just looking at it from a common sense prospective.

Jeff
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#3211433 - 12/09/13 03:47 PM Re: Curious about VI and MRV [Re: Tucson Five-O]
Tucson Five-O Offline


Registered: 05/29/06
Posts: 222
Loc: Tucson, AZ
Caterham,

On a related note, I've always been curious as to whether, comparing two similar oils in the same engine (such as my 1.4L Cruze) on startup at say 32F, such as Mobil 1 AFE 0W-30 with a VI of 166 and a 40C KV of 62.9, vs. Mobil 1 5W-30 with a VI of 172 and a 40C KV of 61.7, which oil would generate higher oil pressure (assuming the oil pump isn't in bypass).

My gut feeling is the lower density AFE (.842 vs. .855) at any comparable oil temperature would generate less oil pressure (albeit slightly) than it's Mobil 5W-30 counterpart, not just at low (below 0F) temperatures. We know that the AFE 3.0HTHSV vs. 3.1 (probably as you have suggested previously is more like 3.08) will be lighter with less resulting oil pressure at 150C fully warmed up in the bearings.

I just am skeptical that AFE is only thinner at extremely low temperatures and at extremely high oil temperatures, but not from, say 0-100C. Otherwise, how can XOM claim fuel economy savings over the oil temperature range where most driving occurs? Unless there are some secret viscometric qualities (easier flowing) that allude our analysis.

Just food for thought (and sorry going off on a tangent, but it's somewhat related to the original question).

Gary
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#3211450 - 12/09/13 04:06 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
CATERHAM Offline


Registered: 11/18/05
Posts: 9448
Loc: Burlington, Ontario, Canada
Originally Posted By: Jeffs2006EvoIX
[quote=CATERHAM][quote=Jeffs2006EvoIX]

Thanks CATERHAM for the info. My application calls for a VW 502 approved oil so I cant use just any 5w30. Most oils in that grade are heavy 30w's like GC.

Just seems to me, that "If" most wear of an engine does indeed occur at start up, wouldnt a lower MRV play a role in reducing wear even in warmer climates?

Not trying to think too much on it, just looking at it from a common sense prospective.
Jeff

As you can see GC which is both lighter at hot operating temp's (lower HTHSV) and has a lower VI than M1 0W-40. Largely because of it's lower VI GC is heavier on start-up even at room temperature.

Forget about MRV! It is simply a measure of pumping viscosity at extremely low temp's, it doesn't apply to you in S.Cal or even me in S.Ont. It has no relevance whatsoever to reducing wear in warmer climates.
_________________________
74 Lotus Europa 5W-50
86 Porsche 928S TGMO 0W-20 25%/M1 0W-40
96 BMW 328i Idemitsu/TGMO 0W-20 70%/M1 0W-40
94 Caterham 7 Sustina 0W-20 80%/0W-50

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#3211451 - 12/09/13 04:08 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
Rand Offline


Registered: 08/20/03
Posts: 7466
Loc: Akron,Ohio
mrv is more important at very cold temps.

also different grades of oil are often tested at different temps for mrv


so a 0w30 might be tested at -40C while a 5w30 is tested at -35C
10w30@ -30C etc.

Since I doubt it gets below 0F in California its not very important/relevant.
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#3211452 - 12/09/13 04:08 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
jrustles Offline


Registered: 02/24/13
Posts: 1977
Loc: Ontario, Canada
Originally Posted By: Jeffs2006EvoIX
So is MRV is better number to be looking at for Cold Start Protection?


More relevant for sure.


Good reading:
Originally Posted By: TomNJ
Hi Madmike,

I would not trust any such formula. Pour point measures the temperature at which the oil stops pouring under its own weight, that is, under low shear conditions. In the engine, oils are sucked and pumped, which is much higher shear conditions and does not correlate to pour point. This is why the specifications call for CCS and MRV viscosity measurements instead of pour point.

Imagine a bowl of Jell-O. If you tilt the bowl, the Jell-O will wobble and perhaps sag a bit, but it does not flow out of the bowl like a liquid. This lack of flow would suggest that the Jell-O is a solid that would not flow where needed. Now take a spoon and stir, and the Jell-O will move fairly freely under the force (shear) of your hand. Then take wide straw and suck the Jell-O - again the Jell-O will flow up the straw under this vacuum force, but it will not flow back into fill the hole you sucked out. In other words, applying a force to an apparent solid material can cause it to flow and pump, even though it cannot do so under its own weight. The reason is that the Jell-O has a weak crystalline structure that breaks easily under force (shear) and reverts back to a liquid like substance that can be easily moved.

A similar situation exists with motor oils since mineral oils have waxes that grow crystals under certain temperature conditions, causing a "freeze point" as opposed to a "pour point". The difference is that "pouring" stops when the viscosity rises to a point that the oil is just too stiff to flow, while "freezing" occurs when the crystal structure from the waxes "knits" the oil into a weak solid, sort of like Jell-O. Crystal growth in oils requires a very slow cool down to occur, often with a pause or soak period. The pour point test cools at a relatively fast rate that can "super cool" the fluid, that is, it whizzes (technical term) right on past its freeze point and runs to its pour point, missing any freezing along the way.

The CCS test stirs the oil (applies shearing force) during the cool down and better simulates the shear rates of the oil pump than a simple pour point. The MRV test cools at a very slow rate with less shear and catches the effect of any freezing tendency.

Back in 1981 Quaker State had an oil that caused over 1,000 engines to seize due to these effects. The oil had a good pour point and CCS viscosity and could be readily sucked up and pumped by the oil pump when cold. However, their VI improver caused crystal growth under certain cooling conditions, turning the oil into a Jell-O like consistency in the pan. Then when the pump sucked the oil up from the reservoir in the pan, it created a hole and the oil was not able to flow back in and fill the hole. The pump then sucked air and the engines seized within minutes from oil starvation. This freezing phenomenon was prevalent and well documented in the Sioux Falls area where the temperatures during the failures cooled very slowly and paused for a while at about +10-15F. When simulated in the lab, the otherwise passing oil exhibited a freezing tendency. This temperature profile was referred to as the "Sioux Falls Cycle" and formed the basis of the cooling cycle used in the MRV test, which was then added to the J300 spec. QS owned up to the problem and paid the claims.

Tom
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#3211458 - 12/09/13 04:21 PM Re: Curious about VI and MRV [Re: Tucson Five-O]
CATERHAM Offline


Registered: 11/18/05
Posts: 9448
Loc: Burlington, Ontario, Canada
Hi Gary,

Since AFE 0W-30 has a lower HTHSV of 3.0cP vs 3.1cP for M1 5W-30 pretty much offsets it's lower VI.
Operational viscosity correlates firstly to HTHSV and secondly to VI. I suspect if you tried the two oils in a vehicle with oil gauges, there would be little noticeable oil pressure difference between them at temp's above freezing. AFE may be very slightly lighter but that would be giving some credit to Mobil's claim of higher fuel economy with AFE.
As temp's drop below freezing, that's when AFE will become comparatively lighter and very much so at extremely low temp's.
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#3211533 - 12/09/13 05:41 PM Re: Curious about VI and MRV [Re: Jeffs2006EvoIX]
OVERKILL Online   content


Registered: 04/28/08
Posts: 26106
Loc: Ontario, Canada
Originally Posted By: Jeffs2006EvoIX


As stated by Gary PU 5w40 Euro does have less VI but a better MRV

Jeff


No it doesn't. The MRV for a 5w-40 and a 0w-40 aren't measured at the same temperature (assuming this is what you were comparing with the above statement). MRV and CCS basically double for every 5C in temperature from what I've observed, so whatever the MRV for PU 5w-40 is, double it to compare to M1 0w-40.
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