Question: What is molybdenum’s real role?

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@High Performance Lubricants sorry but I wanted to chase down several loose ends with hopefully a definitive answer; I’ll try to summarize as much as possible.

We’ve all seen and heard that moly is a friction reducer; there is plenty of documentation here already on that. One would assume that with friction reduction, there would also be wear reduction. While some of us know that UOAs are not a valid wear measurement tool, there have been same engine type/ same owner samples that may show an oil with 2x/3x/5x for example more moly, yet the entire UOA can look essentially identical otherwise. This doesn’t make sense on its surface considering the trimer/dimer moly’s have plenty of proof that they are extremely “slippery”. Thoughts?

However, many who have gone to a high moly oil (Idemitsu, Redline, HPL, or even some who add MoS2 or Lubegard BioTech) nearly all mention their engines sounding “quieter”. We know that moly is a fairly hard metal; I’ve posited (WAG, really) that moly is maybe acting as a “shock absorber” as well and this sacrificial layer is somehow quieting the engine? Or is it possible that the moly is simply filling in some of the asperities between surfaces which then improves the amount of surface area experiencing hydrodynamic lubrication?

What’s HPL’s 10,000’ view on moly since your oils obviously use quite a bit of the good stuff, and any quick anecdotes on why high moly oils don’t appear to offer any wear benefit even when analyzing single-engine trends over multiple UOAs? Thanks!!
 
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Moly is used in conjunction with other friction modifiers for its anti-wear properties.

I believe it was stated that motor oils such as Idemitsu who uses higher concentrations of moly is using MoS2 (Molybdenum Disulfide) where as others uses MoDTC (Molybdenum Dialkyldithiocarbamate), the latter being more oil soluble with MoS2 falling out of suspension.
 
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@High Performance Lubricants sorry but I wanted to chase down several loose ends with hopefully a definitive answer; I’ll try to summarize as much as possible.

We’ve all seen and heard that moly is a friction reducer; there is plenty of documentation here already on that. One would assume that with friction reduction, there would also be wear reduction. While some of us know that UOAs are not a valid wear measurement tool, there have been same engine type/ same owner samples that may show an oil with 2x/3x/5x for example more moly, yet the entire UOA can look essentially identical otherwise. This doesn’t make sense on its surface considering the trimer/dimer moly’s have plenty of proof that they are extremely “slippery”. Thoughts?

However, many who have gone to a high moly oil (Idemitsu, Redline, HPL, or even some who add MoS2 or Lubegard BioTech) nearly all mention their engines sounding “quieter”. We know that moly is a fairly hard metal; I’ve posited (WAG, really) that moly is maybe acting as a “shock absorber” as well and this sacrificial layer is somehow quieting the engine? Or is it possible that the moly is simply filling in some of the asperities between surfaces which then improves the amount of surface area experiencing hydrodynamic lubrication?

What’s HPL’s 10,000’ view on moly since your oils obviously use quite a bit of the good stuff, and any quick anecdotes on why high moly oils don’t appear to offer any wear benefit even when analyzing single-engine trends over multiple UOAs? Thanks!!
You made a statement about the (severe) limitations of $40 UOAs and then proceeded to use $40 UOAs to make a conclusion about the effect of moly on wear metals.
 
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@High Performance Lubricants sorry but I wanted to chase down several loose ends with hopefully a definitive answer; I’ll try to summarize as much as possible.

We’ve all seen and heard that moly is a friction reducer; there is plenty of documentation here already on that. One would assume that with friction reduction, there would also be wear reduction. While some of us know that UOAs are not a valid wear measurement tool, there have been same engine type/ same owner samples that may show an oil with 2x/3x/5x for example more moly, yet the entire UOA can look essentially identical otherwise. This doesn’t make sense on its surface considering the trimer/dimer moly’s have plenty of proof that they are extremely “slippery”. Thoughts?

However, many who have gone to a high moly oil (Idemitsu, Redline, HPL, or even some who add MoS2 or Lubegard BioTech) nearly all mention their engines sounding “quieter”. We know that moly is a fairly hard metal; I’ve posited (WAG, really) that moly is maybe acting as a “shock absorber” as well and this sacrificial layer is somehow quieting the engine? Or is it possible that the moly is simply filling in some of the asperities between surfaces which then improves the amount of surface area experiencing hydrodynamic lubrication?

What’s HPL’s 10,000’ view on moly since your oils obviously use quite a bit of the good stuff, and any quick anecdotes on why high moly oils don’t appear to offer any wear benefit even when analyzing single-engine trends over multiple UOAs? Thanks!!

Friction does not equal wear. Even without friction an engine wears. Abrasive wear, caused by friction isn't the only wear mechanism. But even when we only look at abrasive wear there's no correlation between friction and wear. Phosphate glass has a high friction coefficient (the stuff that zddp lays down) but it wears instead of the metal it's protecting.

MoS2 is very low on the Mohs hardness scale, it's amongst the softest substances around. Quite like graphite, the stuff that pencils are made of and that has trouble tearing up paper....

MoDTC puts another low friction layer on top of the anti-wear layer, it's not going to reduce wear that's not happening anyway but it can reduce friction.
 
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Friction does not equal wear. Even without friction an engine wears. Abrasive wear, caused by friction isn't the only wear mechanism. But even when we only look at abrasive wear there's no correlation between friction and wear. Phosphate glass has a high friction coefficient (the stuff that zddp lays down) but it wears instead of the metal it's protecting.

MoS2 is very low on the Mohs hardness scale, it's amongst the softest substances around. Quite like graphite, the stuff that pencils are made of and that has trouble tearing up paper....

MoDTC puts another low friction layer on top of the anti-wear layer, it's not going to reduce wear that's not happening anyway but it can reduce friction.
I have no specific knowledge of engines but I do have a good understanding of physics so please just see this as an inquiry more than a challenge. I'm really just looking for a more detailed explanation of your statements but let me start with my rationale.

I can't imagine there are ever two metal surfaces that come into close proximity to each other (close enough where the boundary layer is relevant) while moving anywhere in any engine regardless of the lubricant that doesn't have some non-zero friction coefficient. If it has a non-zero friction coefficient then over time the atoms at the surface of these two metal surfaces are wearing away. It may or may not be meaningful over the course of an average OCI or even an average engine lifetime but I see no way that it isn't happening and it is in part (even if it's a tiny part) contributing to the wear metals measured in a UOA.

So if friction isn't the major contributor to wear metals in a UOA then what are the major contributors?
 

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You made a statement about the (severe) limitations of $40 UOAs and then proceeded to use $40 UOAs to make a conclusion about the effect of moly on wear metals.
Nope. I acknowledged the limitations and asked the experts with much better equipment than a $30 UOA uses to tell us what’s really going on. I bolded the “appear” for the people who think that UOAs are a wear measurement tool. 👍🏻
 
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I have no specific knowledge of engines but I do have a good understanding of physics so please just see this as an inquiry more than a challenge. I'm really just looking for a more detailed explanation of your statements but let me start with my rationale.

I can't imagine there are ever two metal surfaces that come into close proximity to each other (close enough where the boundary layer is relevant) while moving anywhere in any engine regardless of the lubricant that doesn't have some non-zero friction coefficient. If it has a non-zero friction coefficient then over time the atoms at the surface of these two metal surfaces are wearing away. It may or may not be meaningful over the course of an average OCI or even an average engine lifetime but I see no way that it isn't happening and it is in part (even if it's a tiny part) contributing to the wear metals measured in a UOA.

So if friction isn't the major contributor to wear metals in a UOA then what are the major contributors?

adhesive, abrasive, fatigue, corrosive.... with the one you're referring to being abrasive wear. corrosive wear happens even whan the engine isn't moving.
 
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adhesive, abrasive, fatigue, corrosive.... with the one you're referring to being abrasive wear. corrosive wear happens even whan the engine isn't moving.
Does one or more mode dominate over the others in an otherwise healthy engine?
 
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Abrasive, in a used engine. But most of the stuff that's worn away should be sacrificial phosphate glass.

Point being, you need to decouple friction from wear, both exist seperately and together. It's also possible to have low friction and high wear, or high friction and low wear.
 

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@SubieRubyRoo what is it about the moly basics summary written by @MolaKule that either isn't clear enough?
Imp, if you read my post closely you’d see I referenced the points in Mola’s summary, AND asked additional questions.

Boiled down, here it is just for you:
1. Moly is slippery and fills in asperities, but where’s the PROOF it is beneficial to the individual user and not just in a lab? There’s immeasurable at best change in mpg, and no statistically significant change in Oil Analysis, so why bother adding an expensive component?
2. Do we really understand why moly appears to make an engine “softer” to the ear- is it because of the moly or the more-complete area that experiences hydrodynamic lubrication or…?

As said here frequently, causation is not correlation, especially when the results are so immeasurable as to be testing “noise”.
 

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Imp, if you read my post closely you’d see I referenced the points in Mola’s summary, AND asked additional questions.

Boiled down, here it is just for you:
1. Moly is slippery and fills in asperities, but where’s the PROOF it is beneficial to the individual user and not just in a lab? There’s immeasurable at best change in mpg, and no statistically significant change in Oil Analysis, so why bother adding an expensive component?
2. Do we really understand why moly appears to make an engine “softer” to the ear- is it because of the moly or the more-complete area that experiences hydrodynamic lubrication or…?

As said here frequently, causation is not correlation, especially when the results are so immeasurable as to be testing “noise”.
And @Imp4 reading the last sentence of Mola’s summary, it would imply that if AN’s and esters are employed in an oil, then moly wouldn’t be needed to keep rings clean?
 
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adhesive, abrasive, fatigue, corrosive.... with the one you're referring to being abrasive wear. corrosive wear happens even whan the engine isn't moving.
These are the 4 wear types defined by physics, but abrasive is the only one that really matters in a modern engine and the only one you can do something about. For the other 3 to be a problem in a modern engine then it was designed incorrectly to begin with and there is not much you can do about it.

My 86 year old father tells me they had a lot more of the other three issues in the 50's. Those aren't the words he uses but that is what he describes. There are a few engines that seem to still have some corrosive issues in the ring area, but its not that common.
 
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No, corrosive wear can easily occur if perfectly good oil is left too long in a perfectly good engine. And a lot easier if there's something wrong with either, like excessive blow-by or low TBN
Oil left too long. Blow by. Low TBN aka used up oil. Corrosive wear in a modern engine rolls its route cause back to another failure or poor maintenance.
 

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Oil left too long. Blow by. Low TBN aka used up oil. Corrosive wear in a modern engine rolls its route cause back to another failure or poor maintenance.
Low TBN could also happen from (possibly errantly!) using a low-SAPS oil in an engine not designed for it. TBN will drop below a useful limit long before the rest of the oil is actually “used up”. 👍🏻
 
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Low TBN could also happen from (possibly errantly!) using a low-SAPS oil in an engine not designed for it. TBN will drop below a useful limit long before the rest of the oil is actually “used up”. 👍🏻
Wouldn't using the properly rated oil at the OEM specified interval would make this failure mode mostly non existent - or is that incorrect?

I am clueless mostly on engine oil chemistry so I am here to be educated. The premise of the OP is does Moly help with Friction wear / prolong engine life as that doesn't seem to be born out in real life examples, and the counter argument was that Friction is only 1 of 4 modes of wear.

Rare exceptions admitted, engine failures due to adhesive, fatigue or corrosive failure are functions of bad design or other root causes - like sticking EGR or lack of maintenance, not engine oil chemistry?

The premise of ILSAC 6B is to lower LSPI - so that's a possible oil failure mode correction for oil outside of friction but that's a fairly new thing for fairly specific engine types, so barring that - I haven't read or seen anything that would change my opinion.

However like I mentioned I am here to be educated, so am happy to change my mind.
 

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Wouldn't using the properly rated oil at the OEM specified interval would make this failure mode mostly non existent - or is that incorrect?

I am clueless mostly on engine oil chemistry so I am here to be educated. The premise of the OP is does Moly help with Friction wear / prolong engine life as that doesn't seem to be born out in real life examples, and the counter argument was that Friction is only 1 of 4 modes of wear.

Rare exceptions admitted, engine failures due to adhesive, fatigue or corrosive failure are functions of bad design or other root causes - like sticking EGR or lack of maintenance, not engine oil chemistry?

The premise of ILSAC 6B is to lower LSPI - so that's a possible oil failure mode correction for oil outside of friction but that's a fairly new thing for fairly specific engine types, so barring that - I haven't read or seen anything that would change my opinion.

However like I mentioned I am here to be educated, so am happy to change my mind.
No sir, I think we’re on the same page essentially. But it does make you wonder as API SP is becoming much closer (and will likely continue to reduce) to a Euro low-SAPS oil- is there a point where older engines will have to drastically shorten the OCIs they were used to on a high-SAPS oil because the TBN will be depleted more quickly? Almost like the ZDDP reduction affected flat tappet cams.

I too don’t know a ton about this and that’s why I posted- the available white papers and summaries seem to show moly is beneficial but stop short of truly explaining the mechanism of improvement and why it seems there’s no objective data to show “better”. I want to learn as well!
 
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