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#3127784 - 09/17/13 04:53 PM What is sulfur's purpose in engine oil?
2000NWXJ Offline


Registered: 08/25/13
Posts: 38
Loc: Oregon
Just want to know what sulfur does (detergent, anti wear, etc.) delo's syn blend says .34%, is this excessive or about average for an hde?
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#3127808 - 09/17/13 05:13 PM Re: What is sulfur's purpose in engine oil? [Re: 2000NWXJ]
hisilver Offline


Registered: 03/08/10
Posts: 530
Loc: NC
Its anti wear. But I thought it was only in gear oil? Shows what I know.

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#3127859 - 09/17/13 06:16 PM Re: What is sulfur's purpose in engine oil? [Re: 2000NWXJ]
Quattro Pete Offline


Registered: 10/30/02
Posts: 25926
Loc: Michigan
Yup, it's part of anti-wear formulation in many oils.
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#3127865 - 09/17/13 06:20 PM Re: What is sulfur's purpose in engine oil? [Re: 2000NWXJ]
JAG Offline


Registered: 10/23/05
Posts: 4532
Loc: Fredericksburg, VA
It comes largely from ZDDP in modern oils. Some types of detergents contain sulfur (ex. calcium and magnesium sulfonates). There are detergents that are sulfur-free like the phenate and salicylate types. It also is in MoDTC (molybdenum dithiocarbomate...thio means sulfur). Group I base oils contain sulfur but given the sparing use of them these days, that source is typically minor or non-existent. 0.34% sounds reasonable amount of sulfur in a HDEO.
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#3127884 - 09/17/13 06:40 PM Re: What is sulfur's purpose in engine oil? [Re: 2000NWXJ]
Errtt Offline


Registered: 11/14/10
Posts: 2143
Loc: California
PQI shows sulfur in some oil but many don't show it.. because it doesn't contain sulfur or they didn't include it in tests I dunno.

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#3127902 - 09/17/13 06:57 PM Re: What is sulfur's purpose in engine oil? [Re: 2000NWXJ]
JHZR2 Offline



Registered: 12/14/02
Posts: 33786
Loc: New Jersey
Yeah its a functional group present on some of the compounds in the oil. Im not sure that the sulfur does much per se, though the theory in diesel fuel lubricity is that sulfur and nickel makes some soft and slippery eutectic compound that wont exist when one takes the sulfur out. I imagine that many of the engine materials do have some Ni in them, so it may be part of the chemisorption or reaction scheme to protect surfaces.

But sulfated ash is a concern for deposits and emissions equipment.

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#3127941 - 09/17/13 07:24 PM Re: What is sulfur's purpose in engine oil? [Re: 2000NWXJ]
MolaKule Offline


Registered: 06/05/02
Posts: 14644
Loc: Midwest
Quote:
Just want to know what sulfur does (detergent, anti wear, etc.) delo's syn blend says .34%, is this excessive or about average for an hde?


That is about the norm for most engine oils.

Sulfur is a natural anti-oxidant.

Sulfur is found mostly as a compound in ZDDP (Anti-Wear and anti-oxidant), MoDTC (Friction modifier), and in the detergents as in Calcium sulfate and Magnesium sulfate.
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#3127966 - 09/17/13 07:44 PM Re: What is sulfur's purpose in engine oil? [Re: JAG]
Tom NJ Offline


Registered: 07/27/06
Posts: 1629
Loc: New Jersey & Virginia
Originally Posted By: JAG
It comes largely from ZDDP in modern oils. Some types of detergents contain sulfur (ex. calcium and magnesium sulfonates). There are detergents that are sulfur-free like the phenate and salicylate types. It also is in MoDTC (molybdenum dithiocarbomate...thio means sulfur). Group I base oils contain sulfur but given the sparing use of them these days, that source is typically minor or non-existent. 0.34% sounds reasonable amount of sulfur in a HDEO.


Excellent explanation.

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#3128163 - 09/17/13 10:57 PM Re: What is sulfur's purpose in engine oil? [Re: MolaKule]
JHZR2 Offline



Registered: 12/14/02
Posts: 33786
Loc: New Jersey
Originally Posted By: MolaKule

Sulfur is a natural anti-oxidant.



Sulfur has a ton of oxidation states, -2 to +6. Not sure what the form is in ZDDP or other PCMO sulfur-containing adds.

But are you saying that the sulfur in these goes to sulfite or sulfate? Or does it just form more bonds to be a sulfone-looking thing?

Has anyone done the IR or even looked at the XANES of the sulfur?

Im writing an article for Langmuir on S k-edge XANES in distillate fuels undergoing treatment. If NSLS wasnt shutting down soon, Id be tempted to try to do some experimentation.

Mola, care to join me for a general user proposal to APS to study this?

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#3128533 - 09/18/13 11:16 AM Re: What is sulfur's purpose in engine oil? [Re: 2000NWXJ]
MolaKule Offline


Registered: 06/05/02
Posts: 14644
Loc: Midwest
I was trying to keep things simple for the non-chemistry people here.

It's the mono-sulfide compounds and di-sulfide compounds that are often used as anti-oxidants.

One has to realize that it is not just elemental sulfur floating around in the oil, rather the sulfur is part of other protective compounds included in the additive package.

Quote:
Mola, care to join me for a general user proposal to APS to study this?


Thanks, but between may dad's cancer situation and the consulting biz, I am quite busy as is.


Edited by MolaKule (09/18/13 11:20 AM)
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#3128713 - 09/18/13 02:51 PM Re: What is sulfur's purpose in engine oil? [Re: MolaKule]
JHZR2 Offline



Registered: 12/14/02
Posts: 33786
Loc: New Jersey
Originally Posted By: MolaKule
I was trying to keep things simple for the non-chemistry people here.

It's the mono-sulfide compounds and di-sulfide compounds that are often used as anti-oxidants.

One has to realize that it is not just elemental sulfur floating around in the oil, rather the sulfur is part of other protective compounds included in the additive package.

Quote:
Mola, care to join me for a general user proposal to APS to study this?


Thanks, but between may dad's cancer situation and the consulting biz, I am quite busy as is.


Sorry to hear about your father.

I guess where I was going was if the sulfur present in the adds in whatever form is sacrificially going to some sort of sulfite or sulfate-type ligand sacrificially? i.e. go from -S- to SOx pulling in the oxygen in the process? Does the sulfur just rearrange bonds and create some kind of sulfone type structure or what? Or is there another mechanism?

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