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#4409110 - 05/19/17 09:56 PM Why does synthetic oil last longer?
Cristobal Offline


Registered: 01/02/11
Posts: 2400
Loc: In The Region Between
I am posting this question for a friend of mine. He is a retired physician and knows more about chemistry than I do.
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#4409124 - 05/19/17 10:15 PM Re: Why does synthetic oil last longer? [Re: Cristobal]
Olas Offline


Registered: 12/11/13
Posts: 3720
Loc: Manchester, England
It depends on which synthetic and which conventional, but, in general;

Syn can last longer because it's generally 'better' at TBN retention, resisting shear, high temp stability, dirt suspension, and all the other metrics that can be used to quantify an oils performance. It's 'custom built' in a lab.
Conventional is kind of a 'close enough' botch job that will do the job but not as well or for as long.
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#4409137 - 05/19/17 10:30 PM Re: Why does synthetic oil last longer? [Re: Cristobal]
Kuato Offline


Registered: 10/23/05
Posts: 6790
Loc: Colorado
yep, and one reason it's so much better is that the carbon chain molecules are all uniform in length. In a non-synthetic you have various lengths; the shorter ones can burn off more easily, the longer ones are thicker and can cause sludge.
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#4409139 - 05/19/17 10:33 PM Re: Why does synthetic oil last longer? [Re: Cristobal]
aquariuscsm Offline


Registered: 12/30/06
Posts: 16491
Loc: South Texas,USA
Don't most synths have a higher starting tbn?
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#4409163 - 05/19/17 11:35 PM Re: Why does synthetic oil last longer? [Re: aquariuscsm]
901Memphis Offline


Registered: 08/14/10
Posts: 12633
Loc: Northern Kentucky
Originally Posted By: aquariuscsm
Don't most synths have a higher starting tbn?


Yes the synthetics get a higher treat rate on additives usually to go with the improved base oils.
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#4409184 - 05/20/17 12:16 AM Re: Why does synthetic oil last longer? [Re: Cristobal]
CT8 Offline


Registered: 10/09/14
Posts: 9103
Loc: Idaho
Define which syn base oil or blend because all syn oils are not equal and gp III oils are better refined than gp II oils which cleaner that base 1 oils due to the higher refining levels [if I worded it properly]. This isn't the 1970's oils anymore.

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#4409200 - 05/20/17 01:20 AM Re: Why does synthetic oil last longer? [Re: Kuato]
FordCapriDriver Offline


Registered: 10/22/15
Posts: 2091
Loc: Balearic Islands , Spain
Originally Posted By: Kuato
yep, and one reason it's so much better is that the carbon chain molecules are all uniform in length. In a non-synthetic you have various lengths; the shorter ones can burn off more easily, the longer ones are thicker and can cause sludge.

I made a post about this a few months back and pretty much everybody agreed that it's just a [censored] marketing strategy.
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#4409209 - 05/20/17 02:31 AM Re: Why does synthetic oil last longer? [Re: Cristobal]
L_Sludger Offline


Registered: 10/04/09
Posts: 3935
Loc: Ohio
Synthetic oil has better marketing. Type SN oil will be virtually indistinguishable from synthetics over the life of a motor. And it better be, because its three times as expensive as Type SG used to be, and costs what synthetic used to cost!
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#4409210 - 05/20/17 02:31 AM Re: Why does synthetic oil last longer? [Re: Cristobal]
Gokhan Offline


Registered: 12/29/10
Posts: 2846
Loc: Los Angeles, California
The difference between synthetic oil and conventional oil is the base oil. Additive packages are the same.

Primarily, the reason synthetic oil lasts longer is because its base oil oxidizes (cooks) slower. However, there are different synthetic base oils with different oxidation resistance.

Secondarily and much less importantly, synthetic oils tend to have less viscosity-index-improver (VII) polymers, which helps reduce permanent viscosity loss in used oil as well as polymer contribution to dirt and sludge, which also helps increase the oil-change interval.
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#4409237 - 05/20/17 04:47 AM Re: Why does synthetic oil last longer? [Re: Cristobal]
SR5 Offline


Registered: 07/07/15
Posts: 3504
Loc: Down Under
Yes as Gokhan says, a synthetic base oil be it Group 3 or Group 4, offers better oxidation resistance than mineral base (Group 1 or Group 2) oil. Not that many oils use Group 1 anymore.

Also synthetics have a naturally higher viscosity index (VI) so less polymer VII (Viscosity index improver) is required and so there is less to shear or break down and form deposits. Given the same grade of oil, eg 5W30.

Most synthetics tend to have a better add pack, but this more marketing (put all the good stuff together) but obviously this isn't strictly required and there will be exceptions.


Edited by SR5 (05/20/17 04:51 AM)
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#4409239 - 05/20/17 05:04 AM Re: Why does synthetic oil last longer? [Re: FordCapriDriver]
dlundblad Offline


Registered: 09/30/13
Posts: 8485
Loc: Midwest
Originally Posted By: FordCapriDriver
Originally Posted By: Kuato
yep, and one reason it's so much better is that the carbon chain molecules are all uniform in length. In a non-synthetic you have various lengths; the shorter ones can burn off more easily, the longer ones are thicker and can cause sludge.

I made a post about this a few months back and pretty much everybody agreed that it's just a [censored] marketing strategy.


I would have to agree with this as well.
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#4409264 - 05/20/17 06:18 AM Re: Why does synthetic oil last longer? [Re: L_Sludger]
Kamele0N Offline


Registered: 02/09/15
Posts: 1449
Loc: Slovenia
Originally Posted By: L_Sludger
Synthetic oil has better marketing. Type SN oil will be virtually indistinguishable from synthetics over the life of a motor. And it better be, because its three times as expensive as Type SG used to be, and costs what synthetic used to cost!


Well it depends.......modern motocycle SG oils are often more expensive then automotive SN oils....
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#4409278 - 05/20/17 06:45 AM Re: Why does synthetic oil last longer? [Re: Cristobal]
Vern_in_IL Offline


Registered: 06/25/14
Posts: 1641
Loc: IL
My understanding is that Synthetic oils resist shear more, better cold flow characteristics, and can take the heat better. Which is why they are very advantageous in a air cool shared engine/transmission motorcycle.

I think there is more base stock in synthetic oil, (Silkoline pro comp) and the fact that "true synthetic" is made in a lab with more uniformed molecules.


Edited by Vern_in_IL (05/20/17 06:50 AM)
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#4409286 - 05/20/17 07:05 AM Re: Why does synthetic oil last longer? [Re: FordCapriDriver]
tig1 Offline


Registered: 01/03/09
Posts: 12757
Loc: Illinois
Originally Posted By: FordCapriDriver
Originally Posted By: Kuato
yep, and one reason it's so much better is that the carbon chain molecules are all uniform in length. In a non-synthetic you have various lengths; the shorter ones can burn off more easily, the longer ones are thicker and can cause sludge.

I made a post about this a few months back and pretty much everybody agreed that it's just a [censored] marketing strategy.


You and everyone else are wrong.

https://mobiloil.com/en/article/car-main...cVsConventional


Edited by tig1 (05/20/17 07:08 AM)
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#4409359 - 05/20/17 08:47 AM Re: Why does synthetic oil last longer? [Re: Cristobal]
ARB1977 Offline


Registered: 06/12/05
Posts: 4877
Loc: North Texas
Magic
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