Fresh Oil = Stripped AW ???

[Jim Allen]

Originally Posted By: TFB1


As already mentioned, I consider this more wear just after a OC as lunacy...


Have you read the paper or are you dismissing a scientific study just because? Are you also a member of the Flat Earth Society? You brought the term "lunacy" into this discussion.... ?

 

[TrevorS]

Originally Posted By: demarpaint
I read here a while back that the fresh oil with the fresh add pack does some cleaning of deposits that accumulated during the prior OCI. That cleaning frees up wear metals that might have been trapped in those deposits. That could be the cause for a slight spike in wear metals early on in the OCI. That also made sense to me.


That doesn't make sense to me.

As per the paper, oci's from 3k to 12k had lower wear rates and these rates stayed constant from oci to oci.

 

[SlipperyPete]

Originally Posted By: 2010_FX4
There are enough UOAs for different engines at different OCIs to prove this out to a point. Wear is always greater when the oil is new and tapers off as the oil ages. Whether it is due to the AW layer being stripped is debatable, but the fact that a longer OCI until the point of condemnation produces less wear metals is not. Look at some UOAs and you will see it for yourself.


I wonder if fresh oil has a greater capacity to hold wear metals in suspension than older oil.

 

[CATERHAM]

Originally Posted By: Jim Allen
Originally Posted By: TFB1


As already mentioned, I consider this more wear just after a OC as lunacy...


Have you read the paper or are you dismissing a scientific study just because? Are you also a member of the Flat Earth Society? You brought the term "lunacy" into this discussion.... ?

I would love to read the entire SAE paper not just the synopsis.

But to first address the OPs question, fresh oil does not entirely strip away the AW additives that have already been plated on engine parts. The fresh detergents will simply compete somewhat more effectively with the AW additives in the oil but the AW additives will still continue to plate on metal once the oil temp's are high enough to activate them.

As it stands I take the conclusion of the SAE paper that used oil provides less wear with grain of salt.
What I would really like to know are the mechanisms at play.

Is the issue the active level of Ca and/or Mg in the oil in which case using an oil with a low initial TBN should be worthwhile?
Is the mentioned lower viscosity of the used oil contributing to the lower wear numbers?
It worth noting that the paper was just about wear numbers takes from oil samples not actually measured engine wear consiquently there are a number of scenerios that can explain that.

It should be remembered that we are just talking about a few ppm of wear metal differences between new oil and used, nothing that's going to make any difference to the life of an engine compared to all the other variables that do seriously affect an engine's life.

I'm against wastefully changing out an oil prematurely although in some applications an oil can be done in as little as 1,500 miles or less. Motorcycles that share the engine oil with the gearbox is a good example of this.
At the end of the day I will always prefer fresh clean oil to used oil and prefer to err on the side of changing the oil out earlier than necessary than leaving it in too long.

 

[147_Grain]

Originally Posted By: CATERHAM
I will always prefer fresh clean oil to used oil and prefer to err on the side of changing the oil out earlier than necessary than leaving it in too long.



+1

 

[Shannow]

Originally Posted By: CATERHAM
Is the mentioned lower viscosity of the used oil contributing to the lower wear numbers?

Yep, that would be it !!!

 

[Sunnyinhollister]

If the AW layer is chemically "stripped" off by the fresh detergents, than what is to say that the iron surfaces of the engine are also being chemically "stripped" off and thereby contributing to the increase in iron that is being reported in the UOA?

If so are we really seeing an increase in wear? Is the SAE paper based on UOA, tear down measurements, or lab based wear measurements?

Also, if the detergency is depleted, are we now talking about the choice between a potential increase of harmful deposits in the engine and ring packs vs. lower wear numbers?

A lot to ponder.

More coffee is in order

 

[demarpaint]

Originally Posted By: CATERHAM



I would love to read the entire SAE paper not just the synopsis.

But to first address the OPs question, fresh oil does not entirely strip away the AW additives that have already been plated on engine parts. The fresh detergents will simply compete somewhat more effectively with the AW additives in the oil but the AW additives will still continue to plate on metal once the oil temp's are high enough to activate them.

As it stands I take the conclusion of the SAE paper that used oil provides less wear with grain of salt.
What I would really like to know are the mechanisms at play.

Is the issue the active level of Ca and/or Mg in the oil in which case using an oil with a low initial TBN should be worthwhile?
Is the mentioned lower viscosity of the used oil contributing to the lower wear numbers?
It worth noting that the paper was just about wear numbers takes from oil samples not actually measured engine wear consiquently there are a number of scenerios that can explain that.

It should be remembered that we are just talking about a few ppm of wear metal differences between new oil and used, nothing that's going to make any difference to the life of an engine compared to all the other variables that do seriously affect an engine's life.

I'm against wastefully changing out an oil prematurely although in some applications an oil can be done in as little as 1,500 miles or less. Motorcycles that share the engine oil with the gearbox is a good example of this.
At the end of the day I will always prefer fresh clean oil to used oil and prefer to err on the side of changing the oil out earlier than necessary than leaving it in too long.



I agree. I also take it with a grain of salt. Definitely a lot to ponder.

 

[Zaedock]

I have never heard that new oil "strips" AW additives from the previous change.

The new oil's additive package takes time to fully activate (how much time- I guess would depend on the oil/engine/conditions). Knowing this, I would think that the existing AW layers are simply depleted from use (not stripped), causing a small period of "wear".

 

[Ken2]

Keep in mind that the oil analysis does not measure wear. Wear is measured with measuring instruments or by weighing the used part vs. its weight when new.

Oil analysis measures the particles in the oil sample. It can't determine how the particles got there.

The antiwear layer is plated on the metal and bonded to the metal's crystalline structure. The "thio" in the antiwear agent is sulfur which helps form this bond.

 

[Nickdfresh]

Originally Posted By: Jim Allen
Originally Posted By: TFB1


As already mentioned, I consider this more wear just after a OC as lunacy...


Have you read the paper or are you dismissing a scientific study just because? Are you also a member of the Flat Earth Society? You brought the term "lunacy" into this discussion.... ?


It may have been "scientific" if it was peer reviewed. But there is a good deal of conjecture and opinion as well.

I recall a lot of this theory is based on a study done by Ford Motor Company in the 1970's on Pintos where new oils showed higher wear numbers. But part of the problem here is that UOA's are not particularly scientific necessarily and some here do hold the contrarian opinion that the oil has higher wear numbers simply because the elements in the oil lift up deposits causing a spike...

 

[turtlevette]

I don't buy it. If a detergent is aggressive enough to attack metals, it doesn't belong in the oil.

I can't believe lubrication engineers would allow that to happen. Especially in this day and age.

 

[Errtt]

So if some AW properties are lost temporary when doing a fresh oil change, then its safe to say not only those that do very short OCIs, normal, not severe duty, are not getting use of the oil, loosing money buy not getting full use of the oil (and filters most cases), but not doing the engine(s) any good although they like to keep the oil looking good and fresh? - actually are doing more harm then good? engine wise

 

[Jim Allen]

A lot of assumptions here made by people who have not read the paper (and there are other similar ones) or heard a real tribologist talk about it. You can't debate what you haven't read.

 

[Garak]

Originally Posted By: Phishin
Out of those 17k miles, I've done AT LEAST 30 oil changes. I've never gone past 600 miles!! This engine spins between 9k-10.5k over 90% of it's life.

Yes, it's a scooter and it's only 50 ccs. Maybe it absolutely beats the heck out of the oil, too. Such equipment is usually not known to be easy on oil.
Originally Posted By: turtlevette
I don't buy it. If a detergent is aggressive enough to attack metals, it doesn't belong in the oil.

Most of the detergents are metals.

Nonetheless, attacking the AW layer is not the same thing as attacking the engine, either.

 

[GMorg]

In the thread below, Molekule and bruce381 went for "new is always better". The literature suggested otherwise then and now. I'm with Jim Allen and the literature on this one. However, I think that changing oil too soon is much better for your engine than changing too late.

In regard to metal accumulation in the oil early verses late, Molekule suggest that fresh detergents may clean some gunk out. The tribological layer was not addressed then.

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/179231/1

 

[Shannow]

Originally Posted By: turtlevette
I don't buy it. If a detergent is aggressive enough to attack metals, it doesn't belong in the oil.

I can't believe lubrication engineers would allow that to happen. Especially in this day and age.


It's not "attacking" metals...the more different species you have present, the less any one of them has a chance to dominate the films formed.

http://home.physics.wisc.edu/gilbert/publications/101.PDF

Gives a good idea what "competing" chemistries get up to.

Deserves (and will get it's own thread in the papers section)

 

[Clevy]

Originally Posted By: Phishin
I've seen this mentioned many times the past few weeks. Makes no sense to me.

People claim that fresh oil strips their engine of AW additives like ZDDP and Moly.

So using this theory, do AW additives just not "stick" until oil gets older? LOL!!!! What kinda myth is this line of garbage?



The new old strips the old oils anti-wear. Read the bitog homepage. The S.A.E. Say it is so,so I suggest you mention to them their research and conclusions are garbage.
And if you actually think about it it makes sense.
The new oil cleans everything the old oil has left behind then applies its own anti-wear layer.
If this action didn't take place moving parts would get layer upon layer of stuff stuck too it,then we'd call it varnish.
Try reading dnewtons articles on the homepage. You might learn something.

 

[GMorg]

Shannow,

Doesn't that paper refer to film deposition as opposed to film removal. The suggestion in this thread appears to be that detergents can remove AW films. Since some of the film deposition appears to be covalent (attached through a chemical bond), I don't see how the base of the film could be removed by detergent. I do see how the composition of the new film would be affected by the entire formulation.

 

[JHZR2]

Originally Posted By: Shannow
Originally Posted By: turtlevette
I don't buy it. If a detergent is aggressive enough to attack metals, it doesn't belong in the oil.

I can't believe lubrication engineers would allow that to happen. Especially in this day and age.


It's not "attacking" metals...the more different species you have present, the less any one of them has a chance to dominate the films formed.

http://home.physics.wisc.edu/gilbert/publications/101.PDF

Gives a good idea what "competing" chemistries get up to.

Deserves (and will get it's own thread in the papers section)


Good. A XANES study. XPS would have been better, but good to see an actual physical chemistry/surface science based publication to discuss.