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#2390873 - 09/28/11 09:10 PM Difference between SM & SN
Bamboooo Offline


Registered: 09/11/11
Posts: 252
Loc: Kansas
I did a search, and found a few discussions about SM & SN oils. But, I can't really find a solid answer. What's the difference? What makes a SN a SN? And a SM a SM? What does one have that the other doesn't? Simple to understand answers are greatly appreciated! Thanks
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#2390903 - 09/28/11 09:30 PM Re: Difference between SM & SN [Re: Bamboooo]
kevinf Offline


Registered: 05/08/09
Posts: 137
Loc: Virginia
Improved high temp deposit control for pistons. Improved sludge control and seal compatibility.
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#2390919 - 09/28/11 09:58 PM Re: Difference between SM & SN [Re: Bamboooo]
JRed Offline


Registered: 06/01/09
Posts: 1633
Loc: Virginia
Seems as though almost all SN rated oils contain at least a small amount of molybdenum, maybe some boron.

There are probably other things that've changed that we can't see in a VOA or a UOA, though.
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#2390934 - 09/28/11 10:10 PM Re: Difference between SM & SN [Re: JRed]
mongo161 Offline


Registered: 07/11/10
Posts: 3200
Loc: Coney Island, NY
Then there are some SN oils that have "taken out" or "reduced" the amount of Moly from the SM rated oil. Case in point....take a look at Havoline in SN compared to SM...Where is the Moly? It's all gone in the SN version of Havoline! Take a look again at Valvoline MaxLife, HM, synthetic blend in SM and compare it to the SN. Where is the Moly in the SN? The SM had a nice big dose of Moly and now it's missing from the SN, per VOA results.

Now take a look at PYB SN and SM.....they added a nice healthy dose of Moly to SN, PYB from the previous version of SM.

You also hear all this talk about "Organic" additives, that do not show up on UOA's or VOA's, in the SN oils to replace the metallic add packs in the SM versions. But what are these "Organic" add packs? Seems like it is a trade secret that even the Labs are unaware of in motor oils.

Originally Posted By: JRed
Seems as though almost all SN rated oils contain at least a small amount of molybdenum, maybe some boron.

There are probably other things that've changed that we can't see in a VOA or a UOA, though.
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#2390950 - 09/28/11 10:31 PM Re: Difference between SM & SN [Re: Bamboooo]
chubbs1 Offline


Registered: 06/09/10
Posts: 4574
Loc: Merritt Island FL, USA
Mongo, there still is a pretty nice dose of moly in Maxlife SN. The whole thing is, the additives that the major companies are using are more efficient. Less is needed to achieve the same or better result while protecting emissions systems.
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#2390961 - 09/28/11 10:49 PM Re: Difference between SM & SN [Re: Bamboooo]
dakota99 Offline


Registered: 09/27/09
Posts: 428
Loc: indiana
Mobil has also switched to a balanced Ca/Mg pack. This has been taken both ways. Some think it's a sign of a cheaper product, some say the extra Mg helps it with TBN retention.

UOA's will tell.
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#2390962 - 09/28/11 10:52 PM Re: Difference between SM & SN [Re: Bamboooo]
Bamboooo Offline


Registered: 09/11/11
Posts: 252
Loc: Kansas
Dare I ask? Which is "better"? SM or SN???

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#2390969 - 09/28/11 11:02 PM Re: Difference between SM & SN [Re: Bamboooo]
cmf Offline


Registered: 05/07/11
Posts: 415
Loc: Florida
An oil that meets the SN minimum specs is better than an oil that meets the SM minimum specs. That does not mean that any oil rated SN will be better than any oil rated SM.

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#2390972 - 09/28/11 11:11 PM Re: Difference between SM & SN [Re: cmf]
mongo161 Offline


Registered: 07/11/10
Posts: 3200
Loc: Coney Island, NY
Thanks for clearing that up.
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#2390981 - 09/28/11 11:26 PM Re: Difference between SM & SN [Re: Bamboooo]
Dan55 Offline


Registered: 06/07/08
Posts: 700
Loc: jersey
To simplify the difference SM is GF-4 SN is GF-5 http://sas-origin.onstreammedia.com/orig...derDiagram.html
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#2390988 - 09/28/11 11:39 PM Re: Difference between SM & SN [Re: Dan55]
Bamboooo Offline


Registered: 09/11/11
Posts: 252
Loc: Kansas
Thanks Dan. Just went to the GF-5 website. Lots of info there. here is a excerpt.

Quote:
Improved phosphorous retention (ZDP) to enable emission system durability while maintaining engine protection

Increased levels of organic/inorganic Friction Modifiers to meet improved fuel economy and fuel economy retention

Enhanced emulsion and rust protection for Flex Fuel Vehicle specifically those that run on ethanol based fuel (E85)

Greater seal compatibility to help ensure seal longevity and prevent oil leakage in older vehicles, as demonstrated by a new seal test specifically developed for GF-5
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#2390990 - 09/28/11 11:43 PM Re: Difference between SM & SN [Re: Bamboooo]
mongo161 Offline


Registered: 07/11/10
Posts: 3200
Loc: Coney Island, NY
So if you have a very modern, low friction engine, GF-5 is what you want.

It could be.....The engine clearances might be very small in the new low friction engines, thus the need for GF-5 oils.

So thinner is much better for very modern engines with tight clearances. Less metallic additives, like Moly, help the flow of oil to reach into these narrow passageways for lubrication. The more metallic additives....the thicker the oil.... unless it is all VI.
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#2390998 - 09/29/11 12:12 AM Re: Difference between SM & SN [Re: Bamboooo]
cmf Offline


Registered: 05/07/11
Posts: 415
Loc: Florida
Metallic additives have very little (almost nothing) to do with the thickness of the oil. The length of hydrocarbons in the oil base stock is what determines the thickness of the oil. VII's (viscosity index improvers) and PPD's (pour point depressants) assist in low temperature flowing and pumpability of the oil. VII's can also smooth out the viscosity graphed as a function of temperature.

I have no idea what you are talking about with "modern low friction engines". Modern engines are built with greater precision and tighter tolerances but that has little to do with friction. They can use lighter oil because oil technology and engine technology has improved to the point where film strength is maintained with less viscous oil. That's why people with older cars sometimes use thicker oil, because the increased tolerances of the cylinders makes it so that the thin oil cannot maintain film strength. The only connection between modern engines and friction is that a less viscous oil will provide less resistance which equals better fuel economy.

Viscosity of oil also has nothing to do with it being SM or SN, GF-4 or GF-5.

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#2391006 - 09/29/11 12:29 AM Re: Difference between SM & SN [Re: cmf]
Gene K Offline


Registered: 01/25/03
Posts: 3161
Loc: Decatur AL USA
Originally Posted By: cmf
Metallic additives have very little (almost nothing) to do with the thickness of the oil. The length of hydrocarbons in the oil base stock is what determines the thickness of the oil. VII's (viscosity index improvers) and PPD's (pour point depressants) assist in low temperature flowing and pumpability of the oil. VII's can also smooth out the viscosity graphed as a function of temperature.

I have no idea what you are talking about with "modern low friction engines". Modern engines are built with greater precision and tighter tolerances but that has little to do with friction. They can use lighter oil because oil technology and engine technology has improved to the point where film strength is maintained with less viscous oil. That's why people with older cars sometimes use thicker oil, because the increased tolerances of the cylinders makes it so that the thin oil cannot maintain film strength. The only connection between modern engines and friction is that a less viscous oil will provide less resistance which equals better fuel economy.

Viscosity of oil also has nothing to do with it being SM or SN, GF-4 or GF-5.


We have thinner coated ring packs, coated pistons, roller cams and rockers, coated cam followers, reduced friction cam chains all in production engines. I would say friction has been reduced in modern engines.


Edited by Gene K (09/29/11 12:29 AM)
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#2391011 - 09/29/11 12:41 AM Re: Difference between SM & SN [Re: Bamboooo]
Brons2 Offline


Registered: 09/16/03
Posts: 2484
Loc: Austin, Texas
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