used oil better than new?

[demarpaint]

Originally Posted By: hr1940
There are tribologist that post on a regular basis.

I trust that I will get the best information here due to the fact that the members here study oils and additives even if it is not their chosen field for employment.

Thank you to all the members that help me take care of all my vehicles.

Helen


Thanks Helen! It was one of our resident tribologists, I just wish I would have bookmarked it!

Frank D

 

[MolaKule]

BTW, this same topic and paper and others was discussed at least a year ago.

Quote:
The results demonstrated that under mixed lubrication regimes, the friction performance of engine oil improves with oil aging. However, it can not be assumed that the fuel economy of vehicles would improve appreciably with continued aging. There are other component systems e.g., the piston ring/bore contact, bearings etc.. that operate primarily in the hydrodynamic regime where the viscosity plays a significant role. The viscosity increase associated with oil aging would lead to increased frictional loss at these contacts. Therefore, the net fuel economy gain or loss would depend on the balance of boundary friction decrease with aging and the hydrodynamic friction (due to viscosity increase) increase with increased viscosity due to aging. Also, a remarkable improvement in the wear performance with oil aging in valvetrain contact is encouraging. This could be an enabler for achieving higher oil drain intervals although various other factors need to be considered. However, it would be interesting to know how the wear characteristics of other engine components change with engine oil aging.


Yes, the visosity does increase which provides a slightly thicker hydrodynamic film.

With any study, there are a number of things going on. The wear study appeared to be for cam tappet shims only after run-in of the cam assembly.

I counted at least four different oils as well, so one has to pay close attention to the bookeeping.

One of the oils had a Mag/calcium sulfonate detergent package while another had a calcium packge only (R208). R208 also had had a supplemental AW additive in addition to reduced ZDDP.

Quote:
RO 168 and RO 207 are factory fill oils (MY 2001 and MY 2003, respectively) containing 0.10 wt% phosphorous while RO 206 and RO 208 were developed as prototype GF-4 oils containing 0.05 wt% phosphorous. The formulation of oils RO 168 and RO 207 are similar, with the difference in the detergent system; oil RO 168 contains Ca and Mg sulfonate detergents, while RO 207 contains only the Ca sulfonate detergent. oil RO 206 is similar to oil RO 207 but contains only half of the ZDDP oil RO 208 is similar to oil RO 206 but contains a supplemental antiwear additive.


In addition to an increased viscosity, one of the conclusions was that reduced wear vs. oil aging had to have another cause. The inference is that while ZDDP decomposes, it's the ZDDP decomposition products (phos, sulfur, zinc) that may provide better wear protection as the oil ages.

The thing we don't know is, what is the formulation of these oils. We have to assume these were GroupI/II oils I think.

Most oils contain a bit of ester for seal swell and a fatty acid ester as a friction modifier.

While a good study, one of the questions NOT asked was this: Are these esters polymerizing or transforming under engine conditions with more aging and are they thus providing a thicker tribofilm? Owing to the Chemistry of these components one would have to say yes. Also realize, ZDDP is a Phosphor, sulfur, zinc compounded as an ester as well.

One of the theories I had ( I may not have been the only one with this theory) about early wear was that, due to the greater detergency of the fresh oil, two things would happen: 1. The detergents would strip wear metals and the dispersant would then disperse these metals into the oil, so a short UOA test would most likely show a lot of wear metals not picked up by the low detergency used oil, 2. fresh detergents would also reduce the concentration of AW additives on metal surfaces, thereby allowing temporary wear until the AW additives could compete with the detergents. There is another study that used different detergents with various AW additives, but I can't recall all of the relevant conclusions.

My info is that this study was born out of another previous study to determine how low a concentration of zddp could be tolerated (apparently 200 ppm is the limit), and or how certain (proprietary) supplemental (notice he didn't identify this supplemental) additives affected wwear. It was seen that there was a trend that seemed to show that aging oil was producing lower wear. So the original study was extended (this study) to determine what was happening with the oil and its additive decomposition products.

Much surface analysis using microscopy was done in this study, but what was lacking was an adsorption analysis of the molecular products of the oil. I have to asume that if that data was released, it would show the exact base oil and additive compositions and the cat would have been let out of the bag, I.E., proprietary data.

 

[JHZR2]

+1 Excellent post and analysis.

For the adsorption analysis, would they do a TPD in an inert gas? How would they decide the difference between degraded molecules and induced cracking? What kind of energies are we talking about, what kind of temperatures would the experiments need to be carried out at?

 

[MolaKule]

Good question.

Basically they would do an AA of the new oils and an AA of the aged oils and compare the molecular spectra to determine if any cracking or molecular transformation occurred.

For the exact parameters of the AA and the exact kinematics/thermodynamics, I would have to defer to my
AA collegue.

 

[demarpaint]

Originally Posted By: MolaKule
BTW, this same topic and paper and others was discussed at least a year ago.

One of the theories I had ( I may not have been the only one with this theory) about early wear was that, due to the greater detergency of the fresh oil, two things would happen: 1. The detergents would strip wear metals and the dispersant would then disperse these metals into the oil, so a short UOA test would most likely show a lot of wear metals not picked up by the low detergency used oil, 2. fresh detergents would also reduce the concentration of AW additives on metal surfaces, thereby allowing temporary wear until the AW additives could compete with the detergents. There is another study that used different detergents with various AW additives, but I can't recall all of the relevant conclusions.



Thanks! My memory isn't shot just yet. Someone where on this site is what you posted last year, which made me believe that due to what you mentioned above:

Quote: 1. The detergents would strip wear metals and the dispersant would then disperse these metals into the oil, so a short UOA test would most likely show a lot of wear metals not picked up by the low detergency used oil,

It was that statement that made me believe new oil was getting a bad rap. That and a few other comments you made last year. IMO the jury is still out on this. I still wish I could find that thread!

Thanks for replying!
Frank D

 

[dickwells]

This phenomena was reported by Mechanix Illustrated about 30 years ago. They put new oil in some new cars and used oil in others. The new cars with used oil broke in with less heat build up and wear. Someone needs to come up with a filter system that will take the particulate out of used oil and burn off any lower volatiles so it can just be reused.

 

[friendly_jacek]

Originally Posted By: dickwells
This phenomena was reported by Mechanix Illustrated about 30 years ago. They put new oil in some new cars and used oil in others. The new cars with used oil broke in with less heat build up and wear. Someone needs to come up with a filter system that will take the particulate out of used oil and burn off any lower volatiles so it can just be reused.


Good info. I's a shame how we have to rediscover things like that. I guess places touting frequent oil changes don't want to advertise this effect.

This brings memories about people who would make bypass filters from toilet paper rolls and use oil with good results almost forever.

And finely, it makes the synlube claims less ridiculous as I thought they were.

 

[friendly_jacek]

Originally Posted By: MolaKule

One of the theories I had ( I may not have been the only one with this theory) about early wear was that, due to the greater detergency of the fresh oil, two things would happen: 1. The detergents would strip wear metals and the dispersant would then disperse these metals into the oil, so a short UOA test would most likely show a lot of wear metals not picked up by the low detergency used oil, 2. fresh detergents would also reduce the concentration of AW additives on metal surfaces, thereby allowing temporary wear until the AW additives could compete with the detergents. There is another study that used different detergents with various AW additives, but I can't recall all of the relevant conclusions.


While I don't think I can fully agree with the part 1 (ie, where the wear metals are deposited exactly in for detergents to stip them from? How would that explain the experimental data in the study?), part 2 makes sense as we know detergents are direct antagonists of ZDDP and other AW additives.

But the effect is probably multifactorial.

 

[ekpolk]

Originally Posted By: dickwells
This phenomena was reported by Mechanix Illustrated about 30 years ago. They put new oil in some new cars and used oil in others. The new cars with used oil broke in with less heat build up and wear. Someone needs to come up with a filter system that will take the particulate out of used oil and burn off any lower volatiles so it can just be reused.


The Safety-Kleen oils are suddenly looking better and better...

Incidentally, the AZ store I usually frequent (yes, I admit, I do frequent one...) just started carrying several grades of UPCMO (another new acronym!). But they're selling it for ~$3.50 per quart. Maybe they are ahead of us all.

 

[ekpolk]

Originally Posted By: dickwells
This phenomena was reported by Mechanix Illustrated about 30 years ago. They put new oil in some new cars and used oil in others. The new cars with used oil broke in with less heat build up and wear. Someone needs to come up with a filter system that will take the particulate out of used oil and burn off any lower volatiles so it can just be reused.


That sounds a lot like a good bypass filtration system.

 

[Colt45ws]

3.50? if it was cheap I might consider running it in one of the older cars, just for S&Gs.

 

[friendly_jacek]

Quote:
Against conventional wisdom, engine wear decreases as oil ages to a certain extent, which means that changing your oil more frequently actually causes engine wear; these findings were substantiated by studies conducted by the auto manufacturers and petroleum companies, leading to drain intervals increased from 3,000mi to 5,000-7,500mi in most domestic vehicles.


from http://www.lnengineering.com/oiltesting.html

Looks like this info was not as obscure as I thought. Took me a while to discover it though.
However, this doesn't work in diesels as soot is abrasive and interferes with lubrication.

 

[demarpaint]

So then running oil for 6 months to comply with warranty requirements, draining that oil and using it in another car isn't so far fetched after all. EG: Car is broken in with 20,000 miles it is still under warranty and now driven 100 miles a week. Two 25 mile round trips per week logging ~ 3000 miles in 6 months. The car had plenty of time to burn off any moisture etc, that oil should be perfect for use in another car after being drained into a clean container and strained? At least according to what is being discussed here.

Me, I think MolaKule's first theory still makes sense. JMO

 

[ecco123]

I'd like to ask you a question about this, maybe it will sound stupid to you but, as I don't have any technical knowledge I have the doubt.

Will a very high performance oil intended for long service intervals, like the european super long life or something like that wear the engine more when they are new?

For example: if a regular cheap oil is intended to 6000 miles service intervals is at its best at 3000 miles, would an oil that should be able to perform 50000 miles without being changed (like some big truck engine oils) be at its best at let's say 15000 miles? Then in a conventional car that will never have such a long interval we would never reach its best point.

As for the diesels, in this article they mention the sludge too, so it may not be related only to petrol engines I think.

I guess the oil analisys is the only way to find out for sure.

 

[friendly_jacek]

Originally Posted By: ecco123

For example: if a regular cheap oil is intended to 6000 miles service intervals is at its best at 3000 miles, would an oil that should be able to perform 50000 miles without being changed (like some big truck engine oils) be at its best at let's say 15000 miles? Then in a conventional car that will never have such a long interval we would never reach its best point.


While the study did not address synthetic oils or long service oils. I don't think there should be a difference.

 

[Boomer]

As materials breakdown over time due to heat and shear, you can geta real "witches brew" of organics. I amsure that someone has looked at this via gc/mass spec, ir, nmr, etc. But the longer the oil is run, I would guess the more complex the mixture gets, probably in some time of exponential way based on types of molecules present. Don't forget that even small amounts of metals can act as catalytic sites for hydrocarbon functionaliztion at high temperatures and long times. Shear produces radicals that can emit hydrogen to form alkenes which in turn can rearrange, polymerize, oxidize... You get the point. So the empirical observation is that this brew gives better wear resistance but my guess is that it will be difficult if not impossible to run down the "exact"reason for it as the lubricant stew has become so complex.

 

[bruce381]

also there are maybe 6-10 types of ZDDP in that they can be made of various carbon chain alchols and primary or secondary or teriary alchols all of which "activate' at different temps and give different AO and wear properties.

example as in a ZDDP with high Oxidation protection may need a high temp to activate and may have high wear rates, where a other ZDDP may have a low temp to activate and have low wear rates but lousy AO properties.

Have a chart at work so this is just basic info

bruce

 

[bruce381]

that said I think that over changing oil will over the engines like slighlty increase wear BUT big deal if you go 200k or 201K.


I would perfer a clean internal engine to a coked up one.

I think more problems are made with too long a drian (as in exceding the oils useful life) in that sludge and varnish will cause lots of problems, much more than a slightly small percent rise in wear from doing a short change interval.

In other words change when needed

bruce

 

[MolaKule]

Quote:
While I don't think I can fully agree with the part 1 (ie, where the wear metals are deposited exactly in for detergents to stip them from? How would that explain the experimental data in the study?),


it doesn't explain the experimental data in the study. Someone asked about remembering detergent effects and a discussion of same.

Where would fresh detergents strip them from? Anywhere there is a metal surface, especially where there is low oil flow and low oil turbulence, AKA, nooks and crannies.

Again, I said these were my hypotheses, AKA, educated gueses.

 

[MolaKule]

Quote:
As materials breakdown over time due to heat and shear, you can geta real "witches brew" of organics. I amsure that someone has looked at this via gc/mass spec, ir, nmr, etc. But the longer the oil is run, I would guess the more complex the mixture gets, probably in some time of exponential way based on types of molecules present. Don't forget that even small amounts of metals can act as catalytic sites for hydrocarbon functionaliztion at high temperatures and long times. Shear produces radicals that can emit hydrogen to form alkenes which in turn can rearrange, polymerize, oxidize... You get the point. So the empirical observation is that this brew gives better wear resistance but my guess is that it will be difficult if not impossible to run down the "exact"reason for it as the lubricant stew has become so complex.


Thanks Boomer. Glad to see another chemist on-board.