Another "Taxi" Study: Relationship of Engine Bearing Wear and Oil Rheology 872128

[AEHaas]

1987-11-01 Relationship of Engine Bearing Wear and Oil Rheology 872128

Member OVERKILL referred to this SAE paper, another Taxi test. It is from a 1987 published paper but I felt it was worth reviewing:

One premise they stated was: ...it is not clear that thicker oil films will lead to less bearing wear or longer bearing lifetimes. The relationship between HTHS and MOFT in journal bearings is conflicting with no clear conclusion. (keep in mind this is a 35 year old study).

The first arm of the study ran a Buick 3.8L V6 on a dyno. They tested two different 20 grade, and a 30 and 40 grade oil that were “thought” to be API SF quality. The 40 grade was the reference or control oil. (? fully formulated, commercially available oil?). Oils were changed at 2,500 miles but samples for oil analysis were done at 1,250 miles, mid drain interval samples. Direct engine wear was performed by measuring bearing weights before and after the test. The study could have been made better by first breaking in the engines, then tearing them apart to get before and after weights. I admired their attention to details as measing each half of the bearings revealing that more wear ocurred on the high load sides.

Let me digress. Regarding experimental oils vs commercial oils. A friend who worked in the oil section of Shell said the various sub-departments were compartmentalized and secretive. Almost as though keeping information separate so nobody would know the whole truth and formula of the final product but a select few. And we rarely hear how they did the research in development of these oils. Like Coka Cola, some may have no patent because then everybody would know exactly how they were formulated and produced.

The experiment:
Kinematic viscosities at 100C were: 5W20, oil#1=7.0. 5W20, oil#2=8.6. 10W30, oil#3=10.5 and 10W40, oil#4=15.6.
HTHS at 150C were: oil#1=2.1. oil#2=2.5. oil#3=3.0. oil#4=3.3.
Volatilities were interesting, at 375C: oil#1=44. oil#2=26. oil#3=17. oil#4=17.

If I read it right they calculated the load of pushing the car down the road at 70 MPH to be 35 HP. The test runs were hard acceleration, cruise, breaking, repeat...Sump temperatures were kept at 115C (240F) and bearing temperatures were thought to be 150C.

Idle oil pressure, PSI: oil#1=8. oil#2=11. oil#3=8. oil#4=11.
At 65 MPH, PSI: oil#1=35. oil#2=40. oil#3=30. oil#4=38.

MOFT at 120C oil temp in the gallery/ 1,500 RPM, 80 ft-lb load: oil#1=0.70. oil#2=0.88. oil#3=1.05. oil#4=0.95.
MOFT at 120C oil temp in the gallery/ 3,000 RPM, 80 ft-lb load: oil#1=0.72. oil#2=0.93. oil#3=1.13. oil#4=0.70.

Results:
The main and connecting rod bearings had essentially the same amount of wear. The “thicker” 20 grade oil and the 30 and 40 grade oils had the same amount of wear. There was a “non dramatic increase” in wear of the thinnest oil. (They say this but comparing weights the thinnest oils had 3 - 4 times the wear of the others with my interpretation of the data. Remember that 3 or 4 times a really low amount of wear is still a low amount of wear). Later in the paper they described the difference as “much higher” with the thinnest experimental oil.

Also interesting is that the oil analysis data reflected the same pattern of wear as the engine breakdowns, in these dyno tested cars. This goes against what many people on this web site think. This test arm is evidence that UOA is a worthwhile means of measuring engine wear.

The Second Arm of the study was in New York City taxi cabs.
There were 9 different oils, each oil was run in 5 different cars. Cabs were a Chevrolet Caprice with a 4.3L V6 that were spec’ed for a 5W30 motor oil. Each cab was run for 100,000 mi.

Variables were HTHS levels from a low of 2.2 (KV at 100C=6.48) to a high of 3.0 (KV at 100C=9.14). Another variable was the use of viscosity index improvers of two types. One was shear-stable and the other was shear-thinning. Bearing wear was determined by weight loss of the bearings and used oil analysis.

Interesting that UOA for this arm of the experiment did not discriminate between oils, nor with bearing wear. This indicating that used oil analysis is of no benefit to evaluate engine wear. Maybe the true value is somewhere between being of no use and being a reliable indicator.

Taxi Cab Results:
They had quite the variety of experimental oils. They stated that "poor quality" ones can show low wear in one engine and high wear in another. But "good oils" show low wear in all engines. Wear was elevated in a third of the thin oil taxis. No abnormal wear was in taxis with higher HTHS. Wear was always comparable in the main and connecting rod bearings. Average vehicle speed and the fraction of time idling did not correlate with wear. They stated that the critical HTHS viscosity is 2.3.

In general, shear-thinning oils performed better than shear stable oils. They kind of wrote this off hinting that commercial formulators are better. Wear was “marginally” higher for the lower viscosity oils and they recommended that oils should have at least a HTHS of 2.6. Oils with VI improvers performed better than without VII. Also, polymer VI improvers had less wear. There was a statistically insignificant increase in wear at the connecting rod in some of the thinner oils.

They concluded that Minimum Oil Film Thickness MOFT does not discriminate oil performance as good as the laboratory viscometric HTHS measurement. All but the two thinnest oils, out of the nine tested, provided adequate protection.

My Dig:
Once again we are investigating before the thrust of the 20 grade requiring vehicles. The 20 grade oils have come a long way since this experiment. The oils used here were experimental and even the investigators admit that they cannot duplicate the performance of fully formulated commercial oils.

For those who keep referring to the “Taxi Study” proving that an oil must have a HTHS of at least 3.5 to be usable, this is not showing that. The critical value based on these thinnest of experimental, non fully formulated, API SF-ish oils is a HTHS of 2.3.

If your application is always lighter than the maximum design level, you should be able to use a thinner modern oil. Certainly one grade in either direction is not a big change. Who wants to try 4 or 5 grades lower?

ali

My previous Taxi review:
https://bobistheoilguy.com/forums/threads/the-frequently-quoted-taxi-study-sae-2005-01-3818.364101/

 

[OVERKILL]

1987-11-01 Relationship of Engine Bearing Wear and Oil Rheology 872128

Member OVERKILL referred to this SAE paper, another Taxi test. It is from a 1987 published paper but I felt it was worth reviewing:

One premise they stated was: ...it is not clear that thicker oil films will lead to less bearing wear or longer bearing lifetimes. The relationship between HTHS and MOFT in journal bearings is conflicting with no clear conclusion. (keep in mind this is a 35 year old study).

The first arm of the study ran a Buick 3.8L V6 on a dyno. They tested two different 20 grade, and a 30 and 40 grade oil that were “thought” to be API SF quality. The 40 grade was the reference or control oil. (? fully formulated, commercially available oil?). Oils were changed at 2,500 miles but samples for oil analysis were done at 1,250 miles, mid drain interval samples. Direct engine wear was performed by measuring bearing weights before and after the test. The study could have been made better by first breaking in the engines, then tearing them apart to get before and after weights. I admired their attention to details as measing each half of the bearings revealing that more wear ocurred on the high load sides.

Let me digress. Regarding experimental oils vs commercial oils. A friend who worked in the oil section of Shell said the various sub-departments were compartmentalized and secretive. Almost as though keeping information separate so nobody would know the whole truth and formula of the final product but a select few. And we rarely hear how they did the research in development of these oils. Like Coka Cola, some may have no patent because then everybody would know exactly how they were formulated and produced.

The experiment:
Kinematic viscosities at 100C were: 5W20, oil#1=7.0. 5W20, oil#2=8.6. 10W30, oil#3=10.5 and 10W40, oil#4=15.6.
HTHS at 150C were: oil#1=2.1. oil#2=2.5. oil#3=3.0. oil#4=3.3.
Volatilities were interesting, at 375C: oil#1=44. oil#2=26. oil#3=17. oil#4=17.

If I read it right they calculated the load of pushing the car down the road at 70 MPH to be 35 HP. The test runs were hard acceleration, cruise, breaking, repeat...Sump temperatures were kept at 115C (240F) and bearing temperatures were thought to be 150C.

Idle oil pressure, PSI: oil#1=8. oil#2=11. oil#3=8. oil#4=11.
At 65 MPH, PSI: oil#1=35. oil#2=40. oil#3=30. oil#4=38.

MOFT at 120C oil temp in the gallery/ 1,500 RPM, 80 ft-lb load: oil#1=0.70. oil#2=0.88. oil#3=1.05. oil#4=0.95.
MOFT at 120C oil temp in the gallery/ 3,000 RPM, 80 ft-lb load: oil#1=0.72. oil#2=0.93. oil#3=1.13. oil#4=0.70.

Results:
The main and connecting rod bearings had essentially the same amount of wear. The “thicker” 20 grade oil and the 30 and 40 grade oils had the same amount of wear. There was a “non dramatic increase” in wear of the thinnest oil. (They say this but comparing weights the thinnest oils had 3 - 4 times the wear of the others with my interpretation of the data. Remember that 3 or 4 times a really low amount of wear is still a low amount of wear). Later in the paper they described the difference as “much higher” with the thinnest experimental oil.

Also interesting is that the oil analysis data reflected the same pattern of wear as the engine breakdowns, in these dyno tested cars. This goes against what many people on this web site think. This test arm is evidence that UOA is a worthwhile means of measuring engine wear.

The Second Arm of the study was in New York City taxi cabs.
There were 9 different oils, each oil was run in 5 different cars. Cabs were a Chevrolet Caprice with a 4.3L V6 that were spec’ed for a 5W30 motor oil. Each cab was run for 100,000 mi.

Variables were HTHS levels from a low of 2.2 (KV at 100C=6.48) to a high of 3.0 (KV at 100C=9.14). Another variable was the use of viscosity index improvers of two types. One was shear-stable and the other was shear-thinning. Bearing wear was determined by weight loss of the bearings and used oil analysis.

Interesting that UOA for this arm of the experiment did not discriminate between oils, nor with bearing wear. This indicating that used oil analysis is of no benefit to evaluate engine wear. Maybe the true value is somewhere between being of no use and being a reliable indicator.

Taxi Cab Results:
They had quite the variety of experimental oils. They stated that "poor quality" ones can show low wear in one engine and high wear in another. But "good oils" show low wear in all engines. Wear was elevated in a third of the thin oil taxis. No abnormal wear was in taxis with higher HTHS. Wear was always comparable in the main and connecting rod bearings. Average vehicle speed and the fraction of time idling did not correlate with wear. They stated that the critical HTHS viscosity is 2.3.

In general, shear-thinning oils performed better than shear stable oils. They kind of wrote this off hinting that commercial formulators are better. Wear was “marginally” higher for the lower viscosity oils and they recommended that oils should have at least a HTHS of 2.6. Oils with VI improvers performed better than without VII. Also, polymer VI improvers had less wear. There was a statistically insignificant increase in wear at the connecting rod in some of the thinner oils.

They concluded that Minimum Oil Film Thickness MOFT does not discriminate oil performance as good as the laboratory viscometric HTHS measurement. All but the two thinnest oils, out of the nine tested, provided adequate protection.

My Dig:
Once again we are investigating before the thrust of the 20 grade requiring vehicles. The 20 grade oils have come a long way since this experiment. The oils used here were experimental and even the investigators admit that they cannot duplicate the performance of fully formulated commercial oils.

For those who keep referring to the “Taxi Study” proving that an oil must have a HTHS of at least 3.5 to be usable, this is not showing that. The critical value based on these thinnest of experimental, non fully formulated, API SF-ish oils is a HTHS of 2.3.

If your application is always lighter than the maximum design level, you should be able to use a thinner modern oil. Certainly one grade in either direction is not a big change. Who wants to try 4 or 5 grades lower?

ali

My previous Taxi review:
https://bobistheoilguy.com/forums/threads/the-frequently-quoted-taxi-study-sae-2005-01-3818.364101/

Thank you for taking the effort to purchase and read through this study.

Also yes, I think your conclusion regarding the merit of UOA's in determining wear (it depends, somewhere between useless and non) is consistent with the consensus, though I will add that their use on here tends to be so varied in terms of lubricant selection, grade and operating profile that it skews it further toward the "useless" side.

As I've noted in several of these sorts of discussions now (and given credit to @Shannow for, since he was the first to share this here), per the Honda study, this 2.6cP minimum for HTHS is consistent with the safe lower limit for traditional bearing design (generally). Once you got much below that, wear increased and risk of damage increased. This is why wider bearings were pursued (by Honda) for engines that spec'd lower than an xW-20, and they also looked at using special coatings to improve durability.

I think there's a pretty valid takeaway regarding your own experiment with an engine that, like these GM 4.3L engines, spec'd a 5W-30. You've gone WAY below the 2.6cP HTHS and have visible metal in the filter. On top of that, your engine is MUCH higher power density and features forced induction as well as direct injection, which has a tendency to dilute the oil with fuel, decreasing viscosity further and negatively impacting the performance of the AW additives.

 

[TiGeo]

Interesting stuff and appreciate the post.

 

[Bill_W]

1987 is a long time ago as you say… over 36 years ago.

 

[OVERKILL]

1987 is a long time ago as you say…

Sure, but HTHS is HTHS, that hasn't changed.

The Honda study was much more recent and had the same conclusion regarding HTHS. I'm waiting for @ZeeOSix and @kschachn to see this, lol.

What I found more interesting was the role of VII in reducing wear. This is something Dave at @High Performance Lubricants has mentioned, that VII, in moderation, is actually a good thing to have in the oil.

 

[AEHaas]

"What I found more interesting was the role of VII in reducing wear. This is something Dave at @High Performance Lubricants has mentioned, that VII, in moderation, is actually a good thing to have in the oil."

Wasn't there a recent thread showing that higher viscosity index was bad?

Ali

 

[OVERKILL]

"What I found more interesting was the role of VII in reducing wear. This is something Dave at @High Performance Lubricants has mentioned, that VII, in moderation, is actually a good thing to have in the oil."

Wasn't there a recent thread showing that higher viscosity index was bad?

Ali

Don't think so? I mean, all things in moderation right. Using a 3cSt base oil and then putting a crapload of VII in it to get a VI of like 230 isn't the same as using the necessary amount of VII to make the spread on a 0W-40.

 

[TiGeo]

"What I found more interesting was the role of VII in reducing wear. This is something Dave at @High Performance Lubricants has mentioned, that VII, in moderation, is actually a good thing to have in the oil."

Wasn't there a recent thread showing that higher viscosity index was bad?

Ali

As I understand it, VII can increase the oil shearing that happens (that's the HPL "No VII" oil/recent threads) but maybe that really doesn't actually matter w/r wear.

 

[OVERKILL]

As I understand it, VII can increase the oil shearing that happens (that's the HPL "No VII" oil/recent threads) but maybe that really doesn't actually matter w/r wear.

And of course there are different grades and types of VII polymers.

 

[wpod]

Taxi use isn't a high loading operation. A Taxi study good is for lots of miles rapidly.

 

[Bill_W]

And of course there are different grades and types of VII polymers.

My guess is there is an improvement in VII now. (The two types mentioned at 1987) Said “in general VII that sheared performed better”

 

[OVERKILL]

My guess is there is an improvement in VII now. (The two types mentioned at 1987) Said “in general VII that sheared performed better”

Well, there's still the range. Typically, they'll use what they can get away with in terms of price/performance. But yes, I expect the quality, overall, has improved since the 80's.

 

[FowVay]

It may be irrelevant but the HT/HS for the 10W-40 oils back then would not meet the minimum 3.5cP set forth in the SAE J300 today. I wonder which 10W-40 they used. This data is all over the place.

Per Mr. Haas' post: "The experiment: HTHS at 150C were: oil#1=2.1. oil#2=2.5. oil#3=3.0. oil#4=3.3. Kinematic viscosities at 100C were: 5W20, oil#1=7.0. 5W20, oil#2=8.6. 10W30, oil#3=10.5 and 10W40, oil#4=15.6.

 

[TheLawnRanger]

I'm not saying I understand all of the report but your takeaways helped. Thanks for the post.

 

[Cujet]

1987 is a long time ago as you say… over 36 years ago.

And yet, that's just before I worked for Mobil Oil's flight department and was involved in some testing of Mobil 254 HTS (high thermal stability) turbine engine oil and SHC100 grease.

They did all sorts of testing, and as a tech, with an engineering background, I was fascinated. They measured wear, not by weight, but with a scanning electron microscope. They knew exactly what worked and what did not.

My point: Even 36 years ago, the quality of the best products was known to be excellent and the testing methods were far superior to UOA results.

 

[TiGeo]

Interesting comments re UOA. I've just used it for pure interest and to be able to plot data and look at trends.

 

[ZeeOSix]

One premise they stated was: ...it is not clear that thicker oil films will lead to less bearing wear or longer bearing lifetimes. The relationship between HTHS and MOFT in journal bearings is conflicting with no clear conclusion. (keep in mind this is a 35 year old study).

More modern testing and results can cerainaly detect a correlation between HTHS viscosity, the resulting film thickness (MOFT) and the wear rates. King Bearing information brought up in the now locked thread clearly shows the relationships between viscosity and MOFT. I don't think you'll ever find any modern study that will show that HTHS and MOFT has no effect or correlation with wear rates between moving/rubbing parts. It''s basic logic that as the HTHS and corresponding MOFT goes to zero that more and more wear will result. Of course, as discussed many times, the AF/AW tribofilm (the film strength) of the oil formulation, and also the engine component material quality, will have an effect on the wear rate seen when parts start rubbing, contacting and wearing. I'm sure the better formulated oils of today result in a better AF/AW package that helps mitigate wear better when the MOFT due to HTHS viscosity fails to keep moving parts adequately separated.

Wear was “marginally” higher for the lower viscosity oils and they recommended that oils should have at least a HTHS of 2.6.

The thinnest oil used back then on the PCMO market when that 1987 study was down was pretty much 5W-20. Per your post info, the two 5W-20 oils had a HTHS at 150C of: oil#1=2.1. oil#2=2.5. Since a HTHS of around 2.5-2.6 cP is the point most shown to start the acceleration of wear rate, it's now a real surprise that only a moderate amount of added wear was measured. Plus, their test methods and measurements were pretty barbaric to what's available today.

There was a study from the SWRI (Southwest Research Institute) posted a few years ago that used their "RATT" (RadioActive Tracer Technology) that measured real time wear rates on different engine components as a function of engine RPM and load scenarios and oil used in the engine. The basic conclusion was the thinner oil resulted in more wear on most of the engine components. I might have a link somewhere to the study ... will have to look on my computer. IIRC, the oil formulation in that study (or maybe it was another study) was the same between the test oils so that only the viscosity factor on wear could be seen. Maybe someone else reading this knows which studies I'm talking about and can chime in with links, etc.

For those who keep referring to the “Taxi Study” proving that an oil must have a HTHS of at least 3.5 to be usable, this is not showing that. The critical value based on these thinnest of experimental, non fully formulated, API SF-ish oils is a HTHS of 2.3.

Is that what the "Taxi Study" concluded, or is that what someone erroneously took away from the study. This is how misinformation is born and spreads.

As has been mentioned many time - even in this 1987 study discussed here - that when the HTHS gets to around the 2.5-2.6 cP range is when wear starts to accelerate. When the xW-16 and thinner oils came out, engine designers started taking measures to use that thinner oil, like wider journal bearings (because the MOFT will be lower), different engine component materials and coating, etc. There is a reason that API put a unique separate API logo/shield on oil bottles, and why ILSAC designated it differently with an A or B suffix when GF-6 came out ... because they don't want people pouring 0W-16 or thinner into any engine not designed for it.

xW-20 is about a low a viscosity (HTSH of 2.5-2.6 cP) that will still work in engines without special design features used for xW-16 and thinner oils and still maintain "acceptable" wear control, Note that thicker oils can be used in these engines calling for xW-16 or less engines - engines are not effected by oils except for using more fuel, but they certainly could be effected by much thinner oils in terms of wear. Using a xW-16 or lower in an engine not specifying for it will most likely result in more wear as shown by many studies. Will it 'blow-up" the engine? ... probably not, but it will cause it to wear out faster.

Interesting that UOA for this arm of the experiment did not discriminate between oils, nor with bearing wear. This indicating that used oil analysis is of no benefit to evaluate engine wear. Maybe the true value is somewhere between being of no use and being a reliable indicator.

Also interesting is that the oil analysis data reflected the same pattern of wear as the engine breakdowns, in these dyno tested cars. This goes against what many people on this web site think. This test arm is evidence that UOA is a worthwhile means of measuring engine wear.

Did they get into the details of what UOA method was used? Any talk how accurate and repeatable they were? Since there seems to be no solid conclusions on the usefulness of the UOA to track wear, it is still questionable IMO. It could stem from the exact UOA methodology used.

Just like the link I posted in the other locked thread (and another thread to IIRC), the instance of where a slight elevated increase in UOA metal ppm counts didn't look like much was going on with the machinery, but when they looked at other signs of evidence (metal in filter, metal inside the machine) it was a whole different story. UOAs don't pick up much even when a lot of destruction is going on due to wear issues.

 

[TiGeo]

More modern testing and results can cerainaly detect a correlation between HTHS viscosity, the resulting film thickness (MOFT) and the wear rates. King Bearing information brought up in the now locked thread clearly shows the relationships between viscosity and MOFT. I don't think you'll ever find any modern study that will show that HTHS and MOFT has not effect or correlation with wear between moving/rubbing parts. It''s basic logic that as the HTHS and corresponding MOFT goes to zero that more and more wear will result. Of course, as discussed many times, the AF/AW tribofilm (the film strength) of the oil formulation, and also the engine component material quality, will have an effect on the wear rate seen when parts start rubbing, contacting and wearing.


The thinnest oil back then used on the PCMO market was pretty much 5W-20. Per you post info, the two 5W-20 oils had a HTHS at 150C of: oil#1=2.1. oil#2=2.5. Since a HTHS of around 2.5-2.6 cP is the point most shown to start the acceleration of wear rate, it's now a real surprise that only a moderate amount of added wear was measured. Plus, their test methods and measurements were pretty barbarice to what's available today.

There was a study from the SWRI (Southwest Research Institute) posted a few years ago that used their "RATT" (RadioActive Tracer Technology) that measured real time wear rates on different engine components as a function of engine RPM and load scenarios and oil used in the engine. The basic conclusion was the thinner oil resulted in more wear on most of the engine components. I might have a link somewhere to the study ... will have to look on my computer. IIRC, the oil formulation in that study (or maybe it was another study) was the same between the test oils so that only the viscosity factor on wear could be seen. Maybe someone else reading this knows which studies I'm talking about and can chime in with links, etc.


Is that what the "Taxi Study" concluded, or is that what someone erroneously took away from the study. This is how misinformation is born and spreads.

As has been mentioned many time - even in this 1987 study discussed here - that when the HTHS gets to around the 2.5-2.6 cP range is when wear starts to exellerate. When the xW-16 and thinner oils came out, engine designers started taking measures to use that thinner oil, like wider journal bearings (because the MOFT will be lower), different engine component materials and coating, etc. There is a reason that API put a unique separate API logo/shield on oil bottles, and why ILSAC designated it differently with an A or B suffix when GF-6 came out ... because they don't want people pouring 0W-16 or thinner into any engine not designed for it.

xW-20 is about a low a viscosity (HTSH of 2.5-2.6 cP) that will still work in engines without special design features used for xW-16 and thinner oils and still maintain "acceptable" wear control, Note that thicker oils can be used in these engines calling for xW-16 or less engines - engines are not effected by oils except for using more fuel, but they certainly could be effected by much thinner oils in terms of wear. Using a xW-16 or lower in an engine not specifying for it will most likely result in more wear as shown by many studies. Will it 'blow-up" the engine? ... probably not, but it will cause it to wear out faster.



Did they get into the details of what UOA method was used? Any talk how accurate and repeatable they were? Since there seems to be no solid conclusions on the usefulness of the UOA to track wear, it is still questionable IMO. It could stem from the exact UOA methodology used.

Just like the link I posted in the other locked thread (and another thread to IIRC), the instance of where a slight elevated increase in UOA metal ppm counts didn't look like much was going on with the machinery, but when they looked at other signs of evidence (metal in filter, metal inside the machine) it was a whole different story. UOAs don't pick up much even when a lot of destruction is going on due to wear issues.

I had aluminum bits in my filter from a timing chain tearing up my timing chain cover from a broken tensioner and the aluminum and iron only rose a small amount. Fortunatley with enough data it stuck out w/r to the long-term averages but it wasn't like it was substantially higher etc. like you may think!

 

[DuckRyder]

At about that time the directive from GMTC was "Don't use 10/40 in anything" the stated case was that the necessary VII made it too unstable. I wish i could have gotten more out of them - if i could have gotten Terry away from Hi Pockets (I think his name was Ed ) - I might know more about how this knowledge came to light.

RE: UOAs - Agree can be useful but here we tend to change things to often, not trend and not look at the totality of the situation in my opinion... Also i am not sure very rigorous sampling procedure are followed. I came by this belief in a discussion about particle counts. I got fairly dirty ISO cleanliness scores using the darling filter at the time. I got accused of everything from out right dishonestly, to stupidity and improper sampling. So i asked a few questions and found out that in some cases people were waiting up to 30 minutes after shut down to take a sample.

So i took a cold sample - want to guess how that cold sample looked? If you guessed a lot like the other samples you would be correct.

Also when particle counts come up in relation to this filter the presented data is filtered omitting my samples and a couple others that don't fit the narrative.

Anyway, I digress UOAs have use, but they aren't the final word, and they are but one piece in the puzzle, there are several blown up engines here that were turning in fine UOAs and a few that were not.

BTW, Ive driven a 4.3l Caprice - i would bet in taxi service they spent a good deal of time over 60% throttle - that are ... um ... not fast at all.

 

[ZeeOSix]

There was a lot more to the oil filter efficiency vs UOA particle count correlation than one person's experience. Just like someone can't show that HTHS has no effect on MOFT and wear, the same holds true for the correlation between filter efficiency and the cleanliness level of the oil. I'm still waiting for the proof that high efficiency filters don't effect the PC cleanliness of the sump compared to low efficiency filters - as many controlled studies show there is a correlation. But that's a whole other discussion.