Diesel Piston Ring and Liner Wear - Compare Oils

[Shannow]

A rig test to measure friction and wear of heavy duty diesel engine piston rings and cylinder liners using realistic lubricants.

http://web.ornl.gov/~webworks/cppr/y2005/pres/117987.pdf

Using ring and liner sections on a reciprocating bench at temperatures up to and including 100C, the authors measure wear of both ring and cylinder liner segments, by volume and mass.

Four different lubricants used, Jet A1, Mineral oil unadditised, and 15W40 both new and used.

The used oil comparison is good because papers are a little rare on that topic.

Again, this is another paper that demonstrates that the used oil produced significantly less wear than the new oil...

 

[andyd]

Why aren't we driving around on used oil?

 

[Shannow]

Other bad stuff happens, like acid formation, dilution, soot loading that must be gotten rid of.

The Paradise garage sampling study showed that even taking out and replenishing a blackstone bottle's worth every 1,000 miles, the oil reaches an equilibrium.

Maybe taking half a sump out every 3,000 miles, and doing a perpetual OCI filters every 15-20 is the most technically correct way of running.

I'm still researching.

 

[Kuato]

I won't pretend to have read the entirety or the math, but am I reading the chart on P215 correctly? It seem to show that cooler oil has a lower coefficient of friction, which to my unschooled brain says it's more slippery.

Plus it is nice to see research showing that older oil allows less wear. It's counterintuitive but we've speculated about it so much...

 

[SandCastle]

Originally Posted By: Shannow
...Again, this is another paper that demonstrates that the used oil produced significantly less wear than the new oil...


What is the technical explanation for this?

 

[Shannow]

Originally Posted By: Kuato
I won't pretend to have read the entirety or the math, but am I reading the chart on P215 correctly? It seem to show that cooler oil has a lower coefficient of friction, which to my unschooled brain says it's more slippery.


That chart shows the effect of viscosity in the boundary/mixed lubrication that exists at the interface.

Less load, thicker oil films.

Colder oil, thicker oil films.

As the load goes up, and temperature goes up, the oil film gets thinner and the friction increases.

 

[Shannow]

Originally Posted By: SandCastle
Originally Posted By: Shannow
...Again, this is another paper that demonstrates that the used oil produced significantly less wear than the new oil...


What is the technical explanation for this?


When oil is new, the ZDDP is new. There is only one "type" of chemical, and it's yet to be reacted by contact with friction surfaces and blowby gasses.

As the oil is used, these molecules get reacted with, and form a range of oxidised species that all have different reaction rates and temperatures at which they form the protective tribofilms.

If you could include 20-30, or a hundred slightly different species in the initial fill, that would be similar.

 

[paulri]

I was surprised at how well the mineral oil did, compared to new oil. Its my understanding that they wanted to use the mineral oil as the typical motor oil, WITHOUT any additives---is this correct? If so, I would have thought that the additives would have provided more protection....

Anyways, in 2 of teh 3 charts (pp. 215-17), the mineral oil did almost as well as the new oil, and in one of them, it fared just a tad better.

 

[friendly_jacek]

yup, i posted about it a long time ago.
it explains why most car makers insists not to change break-in oil for 10,000 miles these days. most BITOGers resist, LOL.

 

[Joe90_guy]

A couple of things...

First, new oils are usually far more aggressive to seal elastomers than used oils. I'm not altogether sure why but it's probably because some of the more active nitogen sites in the ashless dispersant get neutralised. I've always thought that the US practice of changing the oil every 3,000 miles might actually be doing real damage rather than being 'a good thing'.

Secondly, whilst liner & ring wear is important, I'd always sort of assumed that the bulk of the iron you find in used engine oil is there because of cam tip wear (because of the high contact pressures employed?). Had the Jet, Unadditised mineral oil, fresh 15W40, used 15W40 exercise been repeat for cam wear, I might have expected a lot more blue water between the oils with and without ZDDP.

 

[Joe90_guy]

A couple of things...

First, new oils are usually far more aggressive to seal elastomers than used oils. I'm not altogether sure why but it's probably because some of the more active nitogen sites in the ashless dispersant get neutralised. I've always thought that the US practice of changing the oil every 3,000 miles might actually be doing real damage rather than being 'a good thing'.

Secondly, whilst liner & ring wear is important, I'd always sort of assumed that the bulk of the iron you find in used engine oil is there because of cam tip wear (because of the high contact pressures employed?). Had the Jet, Unadditised mineral oil, fresh 15W40, used 15W40 exercise been repeat for cam wear, I might have expected a lot more blue water between the oils with and without ZDDP.

 

[Jetronic]

Don't forget they had the section immersed in oil, the volume of oil is huge compared to what you see in an engine, and no combustion byproducts were added at the time (including heat for the top ring)

This alone can explain the results of the mineral oil vs formulated.

 

[paulri]

Interesting explanations, Joe and Jetronic.

One more thing---it wasn't clear to me what exactly they were calling "used" oil. How many miles, or what kind of useage, had this oil seen?

 

[CT8]

Originally Posted By: friendly_jacek
yup, i posted about it a long time ago.
it explains why most car makers insists not to change break-in oil for 10,000 miles these days. most BITOGers resist, LOL.
That is not why . Tell me that running oil that has high wear metals and combustion by products reduces wear? What about the cam chain wear on the GM engines that had too long oil change intervals?

 

[CT8]

Originally Posted By: Shannow
Other bad stuff happens, like acid formation, dilution, soot loading that must be gotten rid of.

The Paradise garage sampling study showed that even taking out and replenishing a blackstone bottle's worth every 1,000 miles, the oil reaches an equilibrium.

Maybe taking half a sump out every 3,000 miles, and doing a perpetual OCI filters every 15-20 is the most technically correct way of running.

I'm still researching.
Then think of this, install a toilet paper bypass filter ,change the TP every 3000 kilometers add the Qt of make up oil and never change your oil again. ???? It doesn't work out that way all of the time though.

 

[CT8]

Working on Fleet vehicles,the ones that lasted the longest are the ones that had proper maintenance .

 

[Jetronic]

Originally Posted By: paulri
Interesting explanations, Joe and Jetronic.

One more thing---it wasn't clear to me what exactly they were calling "used" oil. How many miles, or what kind of useage, had this oil seen?


a full, regular oci. No miles or hours mentioned, but it was the same oil brand and type as the fresh oil (cummins)

 

[paulri]

Originally Posted By: Jetronic
Originally Posted By: paulri
Interesting explanations, Joe and Jetronic.

One more thing---it wasn't clear to me what exactly they were calling "used" oil. How many miles, or what kind of useage, had this oil seen?


a full, regular oci. No miles or hours mentioned, but it was the same oil brand and type as the fresh oil (cummins)


That's saying a lot. So oil that in most cases would be considered EOL is still able to function, and do so better than the new stuff.

I wish they had a sample size from each category greater than one. I'd love to see more of this. I didn't see any discussion of how much or how many of each they used, so I can only assume it was one of each. Or did I miss anything?

 

[paulri]

I don't doubt that used oil can perform very well. I recall articles linked to here, by teh SAE that said they outperform new oil up to 12,000 miles.

Its my understanding that these studies were for fleet vehicles, which would usually get a lot of freeway driving, wouldn't they?

Has anyone done a study from oil used in engines that did a lot of city, stop and go driving--comparing wear from used oil, to new oil?

 

[Pontual]

Also those ppm of metal in used oil could act like AW additives? The ester theory became object of comedy neh? New Zddp or used and reacted make some difference, too. Besides the soft carbon side of soot acting as solid lubes, too.