# MoS2, MolybdenumDiSulfide: Good & Bad.



## 559056 (Oct 8, 2016)

I just found a post about a product family from a company called "Liquid Moly" and wanted to issue a warning about a very similar named compound, used for a century to reduce friction in heavy machinery.
I don't know if the company, Liquid Moly, sells Molybdenum Sulfide additives or makes claims associated with MoS2's ability to reduce bearing surfaces made of ferrous materials. But, there are very good things to say about this molecule and some stern warnings to issue.

The good news: MoS2 binds to the surface of ferrous metals, like steel, to form a molecular boundary layer with extremely low friction. One can think of Teflon on frying pans, to picture how this substance binds to such surfaces. In heavy machinery, it is used to reduce the friction of gears, in manual transmissions, transfer cases, "open" differentials, and any other place where rubbing metal parts rob the machinery of efficiency. It is often sold in auto parts stores or online as a grease like additive that squirts out of a tube, to be added to gear lube.
So, in open differentials, manual transmissions, and transfer cases where gears and chains mesh together, one can reduce rolling resistance significantly.

The bad news: Because it binds to ferrous metal parts and effectively reduces friction it should never be used where clutch materials are required for the function of the component; such as, limited slip differentials (on most BMW's), automatic transmissions, or in motorcycle transmissions where the clutches are submerged in the same gear oil as the gears. Else, the clutches/bands will stop doing what they are suppose to do; grab. 
The more serious place where unethical companies have marketed MoS2 is as an engine oil additive. Don't use this. Think about that frying pan with Teflon for this picture explanation. As any reciprocating engine operates, tiny amounts of engine oil slips past the rings, clings to the upper cylinder walls and combustion chamber. If it is just oil, it mostly burns away with each stroke. But, the MoS2, in an additive is left behind to bake onto the surfaces. Eventually, this will destroy the sealing of the combustion chamber and wear the rings and valve stems to the point of an engine overhaul. Just as if one baked Teflon on to the same surfaces inside their engine.


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## southcoastguy (Jan 3, 2017)

Glaird said:


> I just found a post about a product family from a company called "Liquid Moly" and wanted to issue a warning about a very similar named compound, used for a century to reduce friction in heavy machinery.
> I don't know if the company, Liquid Moly, sells Molybdenum Sulfide additives or makes claims associated with MoS2's ability to reduce bearing surfaces made of ferrous materials. But, there are very good things to say about this molecule and some stern warnings to issue.
> 
> The good news: MoS2 binds to the surface of ferrous metals, like steel, to form a molecular boundary layer with extremely low friction. One can think of Teflon on frying pans, to picture how this substance binds to such surfaces. In heavy machinery, it is used to reduce the friction of gears, in manual transmissions, transfer cases, "open" differentials, and any other place where rubbing metal parts rob the machinery of efficiency. It is often sold in auto parts stores or online as a grease like additive that squirts out of a tube, to be added to gear lube.
> ...


Thanks for your warning. I hope there aren't posters here who believe that additives are necessary for the health of their engines.


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