Wear vs. oil-filter efficiency: SAE/Amsoil paper

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Originally Posted By: Ducked
Originally Posted By: ZeeOSix
Originally Posted By: Ducked
"the threat they pose is diminished since they are still larger than many of the clearances within an engine. Their size will not allow them to enter the contact areas..."

Trying to picture how that would work, and can't.

Lets say a particle is small enough to get into the oil pump, but arrives somewhere where its too big. Anywhere it arrives it seems likely to be a problem, either due to blockage, abrasion, or both.

For example, say it gets to a bearing but is too big to enter. It can be too big only because it is in contact with a rotating shaft jourmal surface, and it is partially blocking the oilway where it enters the bearing. This does not seem a benign situation.


The particles that are too large to go through a running journal bearing clearance (which is around 5 to 10 microns oil film thickness when the engine is running) probably get spit out the sides of the bearing. Since the particle isn't being "smashed" between two surfaces, then it probably isn't going to cause much if any damage.


That doesn't appear to make much sense.

If they are small enough to "get spit out the sides of the bearing", then they don't seem to be "too large to go through a running journal bearing clearance" and if they are only just small enough to "get spit out the sides of the bearing" then they are exactly being "smashed" between two surfaces".

If they are too big to enter the bearing at all then they are going to block the oilway.


That said, I don't think I've any quarrel with what seems to be the main message (filtration GOOD, dirt BAD) though I havn't read it carefully.


Here's a figure of what a journal bearing looks like when in operation. The minimum clearance (hmin) is going to be around 5~10 microns. Near the top of the bearing where the oil supply comes in will be around 40~50 microns (the bearing oil feed hole will be large, like 3~4 mm). If a particle makes it into the bearing that is larger than hmin, it won't be able to go through (get smashed in) the minimum clearance, but will most likely get carried out of the bearing via the side leakage and not really cause any damage. Obviously, you'd want an oil filter that can filter out at least most of the 40~50 micron particles.

 
Just wondering, with all the rotating and moving parts in a engine, does a large particle remain large or will it break down into smaller particles?
 
To expound on Zee0Six's posts.

The forces that keep the shaft from contacting the bearing are generated by the oil which is moving from the wide area of the "wedge" to the area of MOFT...obviously, the oil being (largely) incompressible isn't all going to fit through the area of MOFT, and increases it's pressure...the excess leaks out the end (side leakage), and is the majority of the oil that enters the bearing.

Yes, it will shift large, "aerodynamically inefficient" particles out the end gap.

SOME of the particles will embed in the bearing surface, although this is largely a factor in the old white metal days, although the modern polymer coated bearings are heading back this way too.

Originally Posted By: PimTac
Just wondering, with all the rotating and moving parts in a engine, does a large particle remain large or will it break down into smaller particles?


Depends on what they are made of and how hard and brittle...
 
Using available data points, apparently the Asian vehicle OEM filter manufacturers (Honda, Toyota, Hyun/Kia, Mitsu) don't put much credence in the 1988 SAE study for their vehicles and engines. 'Generally speaking', Honda and Toyota seem to have solid reputations for reliability and longevity of their engines.

As for the referenced SAE study, been discussed in depth here several times before. DNewton has a different take on it's application and/or correlation (or lack of) to real world use. I'll leave it to him if he chooses to comment on it again. Or a google search of bitog might reveal one those prior discussions with his points.
 
Good addition of info Shannow.

Also to add, another thing to consider is that newer cars have pretty tight bearing clearances. For instance, the Coyote 5.0L V8 in the new Mustang has a crankshaft bearing clearance specification of 0.0010 to 0.0018 inch. 0.0010 inch = 25.4 microns. It would be advantageous to use a filter that was in the higher efficiency realm (95% or better at 20 microns) since bearings that tight that will run with a little less MOFT than higher clearance bearings, which could make them even more susceptible to wear from sub 10 micron particles.

A filter rated at 99% @ 20 microns will catch way more sub 10 micron particles than a filter rated at 50% @ 20 microns, so tighter bearings should benefit more with a higher efficiency oil filter.
 
Regardless of filter, everything else will go first, resulting in said car being sent to the scrapyard with a working engine. I guess I should be worried since I use proselects or OEM quite regularly! LOL
 
Originally Posted By: fdcg27
Your opening post sounds good, as is often the case with your topics, but when subjected to the reality test it makes no sense.
First off, gasoline engines have been running 200K+ for decades using no more than OEM rocks-catcher filters.
Second, the particle range you suggest is huge and there is no full flow filter whether labeled as having synthetic media or not that is particularly efficient in capturing particles smaller than twenty microns or so.
Multiple pass efficiency is of little importance since each pass exposes the bearings to the particles the oil filter didn't catch on the first pass.
Lots of folks in warm, mostly dry places like the one in which you live have old Toyotas just like yours with as many or more miles.
The difference is that they worry about neither oil nor oil filters.
They just drive their old cars and worry about the many more important things most of us experience in life.


Best post in this thread!

Virtually nobody worries a non-issue like BITOG ! I would bet good money that the OEM's don't go deeper into oil filter selection than our OCD members (not the orange can of death reference here).

Good air filter with effective sealing, proper crankcase venting, proper oil with almost any oil filter, no driver inattention to CEL's, and the VAST majority of engines will outlive the body or other critical 'tipping point to disposal' components.

Worry about your body mass index, your glucose tolerance, your retirement savings plans, dog & cat vet visits before what oil filter to use!
 
Originally Posted By: ZeeOSix
Originally Posted By: Ducked
Originally Posted By: ZeeOSix
Originally Posted By: Ducked
"the threat they pose is diminished since they are still larger than many of the clearances within an engine. Their size will not allow them to enter the contact areas..."

Trying to picture how that would work, and can't.

Lets say a particle is small enough to get into the oil pump, but arrives somewhere where its too big. Anywhere it arrives it seems likely to be a problem, either due to blockage, abrasion, or both.

For example, say it gets to a bearing but is too big to enter. It can be too big only because it is in contact with a rotating shaft jourmal surface, and it is partially blocking the oilway where it enters the bearing. This does not seem a benign situation.


The particles that are too large to go through a running journal bearing clearance (which is around 5 to 10 microns oil film thickness when the engine is running) probably get spit out the sides of the bearing. Since the particle isn't being "smashed" between two surfaces, then it probably isn't going to cause much if any damage.


That doesn't appear to make much sense.

If they are small enough to "get spit out the sides of the bearing", then they don't seem to be "too large to go through a running journal bearing clearance" and if they are only just small enough to "get spit out the sides of the bearing" then they are exactly being "smashed" between two surfaces".

If they are too big to enter the bearing at all then they are going to block the oilway.


That said, I don't think I've any quarrel with what seems to be the main message (filtration GOOD, dirt BAD) though I havn't read it carefully.


Here's a figure of what a journal bearing looks like when in operation. The minimum clearance (hmin) is going to be around 5~10 microns. Near the top of the bearing where the oil supply comes in will be around 40~50 microns (the bearing oil feed hole will be large, like 3~4 mm). If a particle makes it into the bearing that is larger than hmin, it won't be able to go through (get smashed in) the minimum clearance, but will most likely get carried out of the bearing via the side leakage and not really cause any damage. Obviously, you'd want an oil filter that can filter out at least most of the 40~50 micron particles.






The crankshaft has counterweights to keep the clearances more even during operation. I think that picture exaggerates. Turn on an electric motor that runs 1750 rpm and imagine the shaft is the crankshaft of a car engine. It spins fast, and 1750 isn't a lot of rpm. At rest though particles in dirty oil could fall into the cavity like the picture shows, ready for the morning start up revving. Main bearing clearances have always been 1 to 2 mils as far as I know. Smaller hard particles cause wear but just slower. This is why I don't extend oil changes. I'll stay going against the grain on that one. Nothing except a bypass filter equals changing the oil.
 
Originally Posted By: ZeeOSix
Originally Posted By: Ducked
Originally Posted By: ZeeOSix
Originally Posted By: Ducked
"the threat they pose is diminished since they are still larger than many of the clearances within an engine. Their size will not allow them to enter the contact areas..."

Trying to picture how that would work, and can't.

Lets say a particle is small enough to get into the oil pump, but arrives somewhere where its too big. Anywhere it arrives it seems likely to be a problem, either due to blockage, abrasion, or both.

For example, say it gets to a bearing but is too big to enter. It can be too big only because it is in contact with a rotating shaft jourmal surface, and it is partially blocking the oilway where it enters the bearing. This does not seem a benign situation.


The particles that are too large to go through a running journal bearing clearance (which is around 5 to 10 microns oil film thickness when the engine is running) probably get spit out the sides of the bearing. Since the particle isn't being "smashed" between two surfaces, then it probably isn't going to cause much if any damage.


That doesn't appear to make much sense.

If they are small enough to "get spit out the sides of the bearing", then they don't seem to be "too large to go through a running journal bearing clearance" and if they are only just small enough to "get spit out the sides of the bearing" then they are exactly being "smashed" between two surfaces".

If they are too big to enter the bearing at all then they are going to block the oilway.


That said, I don't think I've any quarrel with what seems to be the main message (filtration GOOD, dirt BAD) though I havn't read it carefully.


Here's a figure of what a journal bearing looks like when in operation. The minimum clearance (hmin) is going to be around 5~10 microns. Near the top of the bearing where the oil supply comes in will be around 40~50 microns (the bearing oil feed hole will be large, like 3~4 mm). If a particle makes it into the bearing that is larger than hmin, it won't be able to go through (get smashed in) the minimum clearance, but will most likely get carried out of the bearing via the side leakage and not really cause any damage. Obviously, you'd want an oil filter that can filter out at least most of the 40~50 micron particles.






Well, the passage I was quoting refers to particles betweem 25 microns and half an inch as relatively benign. I dunno where the half inch ones are supposed to be coming from, but assuming it isn't a .50 cal Browning they probably aren't going to get through the oil pump screen.

I wonder if the diagram is accurate, because my understanding is/was that hydrodynamic forces centre the shaft, so I'm surprised its as asymmetric as that, apart from maybe at start up or very low speed.

Anyway, isn't any particle, unless its actually trapped between the two surfaces, (in which case its going to be especially damaging) going to go where the oil goes? I can't see why a large particle is going to be particularly or selectively eliminated by side flow out of the bearing, as y'all seem to be implying. If anything, I'd have thought the reverse.
 
Originally Posted By: Ducked
I wonder if the diagram is accurate, because my understanding is/was that hydrodynamic forces centre the shaft, so I'm surprised its as asymmetric as that, apart from maybe at start up or very low speed.
Asymmetry is a consequence of the rotation of the crankshaft and wedge of oil.

Originally Posted By: Ducked
Anyway, isn't any particle, unless its actually trapped between the two surfaces, (in which case its going to be especially damaging) going to go where the oil goes? I can't see why a large particle is going to be particularly or selectively eliminated by side flow out of the bearing, as y'all seem to be implying. If anything, I'd have thought the reverse.
You have it right. The explanations above merely say "some" particles get squirted out the side, while "some" particles create scratch marks. Larger particles do the same; some make it out, some don't. Its those that don't that create problems of course.
 
Originally Posted By: goodtimes
The crankshaft has counterweights to keep the clearances more even during operation. I think that picture exaggerates. Turn on an electric motor that runs 1750 rpm and imagine the shaft is the crankshaft of a car engine. It spins fast, and 1750 isn't a lot of rpm.


Originally Posted By: Ducked
I wonder if the diagram is accurate, because my understanding is/was that hydrodynamic forces centre the shaft, so I'm surprised its as asymmetric as that, apart from maybe at start up or very low speed.


The hydrodynamic film thickness does increases some with RPM, but the journal bearing will never be perfectly re-centered due to RPM. If the oil clearance is 0.002" (50 microns) when the journal is centered, and the MOFT (hmin) is running at 10 microns while rotating, then in that figure you'd have 10 microns at hmin and 90 microns 180 deg from hmin - which is 9 times the clearance opposite hmin. So the figure might not be as exaggerated as it seems.

Here's a chart that shows how MOFT changes with engine RPM and oil viscosity in the big end rod bearing which experiences huge direction change forces each time the piston changes direction at BDC and TDC (ie, no counterweights). The MOFT increases some with increased RPM, but it's still only a fraction of the total oil clearance in the bearing like the figure shows.

 
Originally Posted By: Ducked

Anyway, isn't any particle, unless its actually trapped between the two surfaces, (in which case its going to be especially damaging) going to go where the oil goes? I can't see why a large particle is going to be particularly or selectively eliminated by side flow out of the bearing, as y'all seem to be implying. If anything, I'd have thought the reverse.


Any particle that is too big to go through the minimum oil wedge (hmin) will either get embedded into the bearing surface as it tries to go through the wedge, or most likely get flushed out with the side leakage of the bearing - ie, "go where the oil goes".

If the MOFT is say running at 5 microns, then the particles that are right at 5 microns +/- a few microns would be the ones most likely to cause wear/damage.

It could be that journal bearings are somewhat "self filtering" to a degree in the sense that the side leakage flow washes most of the damaging particles away before going through the oil wedge (Shannow's "aerodynamically inefficient" comment), and that's why engines that use less efficient oil filters (50% @ 20 microns) seem to last a long time. Just a wild thought.
 
Originally Posted By: goodtimes
The crankshaft has counterweights to keep the clearances more even during operation. I think that picture exaggerates. Turn on an electric motor that runs 1750 rpm and imagine the shaft is the crankshaft of a car engine. It spins fast, and 1750 isn't a lot of rpm. At rest though particles in dirty oil could fall into the cavity like the picture shows, ready for the morning start up revving. Main bearing clearances have always been 1 to 2 mils as far as I know. Smaller hard particles cause wear but just slower. This is why I don't extend oil changes. I'll stay going against the grain on that one. Nothing except a bypass filter equals changing the oil.


Nope the counterweights are there to reduce imbalances that cause vibration in the engine assembly, and yes to reduce bearing loads.

Your electric motor analogy is flawed in that the magnetic field and the rotor are applying a torque around the centre of the shaft.

An IC engine creates torque by the push of the pistons through the con-rods, and to the off centre crankshaft, and these forces are massive...do a simple static balance of forces and reactions, and you can see how flawed your analogy is.

Here's (a diesel) engine example for a big end...Oil film thickness and pressure with crank rotation.

The cyclic nature of big ends (and to a lesser extent mains) will have an opening and closing of the minimum clearances with rotation, which WILL allow largeish particles to move through rather than dam up in the wedge.
 
Originally Posted By: Shannow
Originally Posted By: goodtimes
The crankshaft has counterweights to keep the clearances more even during operation. I think that picture exaggerates. Turn on an electric motor that runs 1750 rpm and imagine the shaft is the crankshaft of a car engine. It spins fast, and 1750 isn't a lot of rpm. At rest though particles in dirty oil could fall into the cavity like the picture shows, ready for the morning start up revving. Main bearing clearances have always been 1 to 2 mils as far as I know. Smaller hard particles cause wear but just slower. This is why I don't extend oil changes. I'll stay going against the grain on that one. Nothing except a bypass filter equals changing the oil.


Nope the counterweights are there to reduce imbalances that cause vibration in the engine assembly, and yes to reduce bearing loads.

Your electric motor analogy is flawed in that the magnetic field and the rotor are applying a torque around the centre of the shaft.

An IC engine creates torque by the push of the pistons through the con-rods, and to the off centre crankshaft, and these forces are massive...do a simple static balance of forces and reactions, and you can see how flawed your analogy is.

Here's (a diesel) engine example for a big end...Oil film thickness and pressure with crank rotation.

The cyclic nature of big ends (and to a lesser extent mains) will have an opening and closing of the minimum clearances with rotation, which WILL allow largeish particles to move through rather than dam up in the wedge.

The electric motor example was to get a feel for rpm of a spinning shaft only. Nothing I said in my post was flawed. It's pretty amazing to realize all the pistons and parts are so well balanced that 3000 rpm is nothing. Writing 3000 rpm on a piece of paper and running a spindle at 3000 rpm and seeing it are two different understandings of 3000 rpm. A shaft flailing to one side in a journal will soon start to ruin the journal and the shaft will start vibrating or "knocking." Another experience is to actually try to measure a few microns, say two, and compare that experience to writing the words two microns on a piece of paper. That's only why I said look at an electric motor shaft spinning.
 
They don't flail from side to side...the journal is full of oil, and hydrodynamics and squeeze films stop them from contacting.

I'm pretty familiar with 210 tonnes of stuff spinning at 3,000RPM on ISO32...
 
Originally Posted By: ZeeOSix


If the MOFT is say running at 5 microns, then the particles that are right at 5 microns +/- a few microns would be the ones most likely to cause wear/damage.



Still don't see how that makes sense.

A particle around the MOFT in diameter (if it isn't washed out sideways) will make first contact at around the MOFT.

A particle around the (MOFT + x) in diameter (if it isn't washed out sideways) will make first contact where the gap is around the (MOFT + x)

Since both will result in damage, I can't see a basis for the claim that bigger particles are less damaging, except insofar as they are less numerous, which intuitively I'd guess they probably are.
 
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When you disassemble an engine where does most of the wear occur on a rod bearing? Why? A crankshaft main bearing? Why?
 
Originally Posted By: Shannow
They don't flail from side to side...the journal is full of oil, and hydrodynamics and squeeze films stop them from contacting.

I'm pretty familiar with 210 tonnes of stuff spinning at 3,000RPM on ISO32...


My electric motor statement wasn't directed at you specifically, or your background. Shafts do flail side to side, and when they flail enough, it is heard as bearing knock. One point missed in all this is the crankshaft journal itself is lucky to be within 5 microns roundness and taper. Then the expansion of metals according to temperature. Then the mounting of bearing shells in a block, where a piece of lint in the air could cause more than 5 microns variation in the mounting. Then there is the accuracy of the block journal boring itself. None of these pictures and graphs make any sense to me due to that. How do they even measure 2 microns, it is easy to plot microns on a graph or draw a picture with a 2 micron gap on a piece of paper.
 
Originally Posted By: Ducked
Originally Posted By: ZeeOSix

If the MOFT is say running at 5 microns, then the particles that are right at 5 microns +/- a few microns would be the ones most likely to cause wear/damage.


Still don't see how that makes sense.

A particle around the MOFT in diameter (if it isn't washed out sideways) will make first contact at around the MOFT.

A particle around the (MOFT + x) in diameter (if it isn't washed out sideways) will make first contact where the gap is around the (MOFT + x)

Since both will result in damage, I can't see a basis for the claim that bigger particles are less damaging, except insofar as they are less numerous, which intuitively I'd guess they probably are.


Quote from the SAE study:
"Medium particles are particles measuring 25 micons to 1/2”. While they are of greater concern than large particles because they are more difficult to remove, the threat they pose is diminished since they are still larger than many of the clearances within an engine. Their size will not allow them to enter the contact areas between many components to promote accelerated wear."

They are saying particles 25 microns and larger are still a concern, but their threat to causing damage is less because they are larger than the typical MOFT and can't get swept through the wedge. They can however still cause some damage.

A particle that enters into the journal bearing that is too big to go through the MOFT might cause some or no damage as it come up to the MOFT wedge and gets washed out with the bearing's side leakage. It's possible it could get embedded into the soft bearing material and continue to do some damage, but my thought is most of the particles that are too large to get smashed through the "MOFT ringer" get washed out with the side leakage.

Obviously if a particle is small enough to enter the MOFT wedge and get smashed between the two surfaces at the wedge, then that particle is going to cause more significant damage than the larger one that doesn't go through the wedge and gets spit out the side of the bearing.

It's the particles that get smashed and abrade in the MOFT between the two moving surfaces that do the most damage.

No matter how you look at it, the bottom line is that better oil filtration is better than not.
 
Originally Posted By: CT8
When you disassemble an engine where does most of the wear occur on a rod bearing? Why? A crankshaft main bearing? Why?


If it's wear caused by abrasive particles, the most bearing & journal wear is always going to be in the region of MOFT.
 
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