Confessions of a Recovering Thickie

[siriusc1024]

Yes. In all cases more viscosity provides higher MOFT. Ok? Ok.

The fact is that it's possible to optimize for MOFT with bearing clearance. Clearly it's possible.

At some point enough MOFT is enough. It's enough MOFT by design. Evidence along your line of thinking is that all the cars running 0w-20 should be falling apart, but they aren't.

From here, pros of going up in viscosity:
- More MOFT for more bearing support
- Less likelihood of mixed lubricant condition
- Offset thinning effect due to age and contamination
- Compensate for increased clearances due to wear

Cons:
- reduced mpg and hp
- increased risk of cavitation
- increased oil temps decreasing oil life (keep in mind that the temperature is an average and that the average is along a gradient from the surfaces. Oil is a blend of hydrocarbons of a range of molecular weights. This is why synthetic lasts longer.)

And the final con:

Going up a grade is perhaps no big deal. When enough is enough don't go too much more. WHY?

The likelihood of film breakdown due to lubricant stall is more pronounced due to higher viscosity having higher lag to dynamic conditions. As the load changes the shape of the supporting wedge of oil changes. The oil must conform.

This risk is amplified with tighter clearances (a design feature that increases efficiency).

As an aside about dynamic loading. Dynamic loading is why engines in vehicles driven on a highway last longer than city/mixed driven. More changing load conditions with city driving than cruising on the highway.

Dynamic loading and hydrodynamic lag is THE REASON why thick can be too thick.

 

[ZeeOSix]

Within the normal operation envelope, running thick oil in a tight clearanced engine spec'd for light oil may increases the risk of metal-metal contact.

MOFT in a dynamic situation is related to clearance. If the oil is too thick it can't flow in a tighter clearance to maintain MOFT as the load changes.

Wrong and wrong ... this has been covered already and shown why it's not true. Go read SubsTech website.

 

[siriusc1024]

Wrong and wrong ... this has been covered already and shown why it's not true. Go read SubsTech website.

Whatever dude. You can't even show why it's wrong. You just keep saying nuh-uh. I used your own graphs to demonstrate what you laughed about - engines are designed with a viscosity in mind.

I answered the big question many people have, including me. Is too thick bad? Yes. It potentially increases wear over time due to higher risk of metal-metal contact as a result of film breakdown.

You go read a book.
https://www.researchgate.net/public...ress_Fluids_with_Pressure-Dependent_Viscosity

 

[ZeeOSix]

Yes. In all cases more viscosity provides higher MOFT. Ok? Ok.

The fact is that it's possible to optimize for MOFT with bearing clearance. Clearly it's possible.

At some point enough MOFT is enough. It's enough MOFT by design. Evidence along your line of thinking is that all the cars running 0w-20 should be falling apart, but they aren't.

Show me where I've said that? I never have, so don't start making things up about what I said here. From the get-go, I've simply said that more viscosity gives more MOFT and that gives more wear protection headroom. I've said it about 20 times, but seems you can't grasp that simple logic. I've also said that going up a grade on anything that specs a xW-20 or less is a no-brainer if someone wants to add some wear protection. So don't start making stuff up about what I've said or claimed.

From here, pros of going up in viscosity:
- More MOFT for more bearing support
- Less likelihood of mixed lubricant condition
- Offset thinning effect due to age and contamination
- Compensate for increased clearances due to wear

Cons:
- reduced mpg and hp
- increased risk of cavitation
- increased oil temps decreasing oil life (keep in mind that the temperature is an average and that the average is along a gradient from the surfaces. Oil is a blend of hydrocarbons of a range of molecular weights. This is why synthetic lasts longer.)

And the final con:

Going up a grade is perhaps no big deal. When enough is enough don't go too much more. WHY?

The likelihood of film breakdown due to lubricant stall is more pronounced due to higher viscosity having higher lag to dynamic conditions. As the load changes the shape of the supporting wedge of oil changes. The oil must conform.

This risk is amplified with tighter clearances (a design feature that increases efficiency).

View attachment 281064

As an aside about dynamic loading. Dynamic loading is why engines in vehicles driven on a highway last longer than city/mixed driven. More changing load conditions with city driving than cruising on the highway.

Dynamic loading and hydrodynamic lag is THE REASON why thick can be too thick.

^^^ Out of context crap. If that was happening in ICE it would be all over the place and discussed all over the place with technical articles wrt to ICE. It not.

 

[siriusc1024]

Show me where I've said that? I never have, so don't start making things up about what I said here. From the get-go, I've simply said that more viscosity gives more MOFT and that gives more wear protection headroom. I've said it about 20 times, but seems you can't grasp that simple logic. I've also said that going up a grade on anything that specs a xW-20 or less is a no-brainer if someone wants to add some wear protection. So don't start making stuff up about what I've said or claimed.


^^^ Out of context crap. If that was happening in ICE it would be all over the place and discussed all over the place with technical articles wrt to ICE. It not.

You never said that. It's something you'd say. Kind of how you're like "all the engines running thicker weights..."

Going up a grade? Potential benefits. Depends on many factors. Not going up two grades for no reasons other than more MOFT = more better. Like those people saying ignore silly VW and to recommend 0w-40 502 in engines spec'd 0w-20 508 for regular street vehicles.

Let me give you the context. Wear over time. Transient conditions of quick metal-metal contact adding up. 150k instead of 275k. Not catastrophic failure. When film breaks down, additives like molybdenum and zddp take over.

 

[ZeeOSix]

Whatever dude. You can't even show why it's wrong. You just keep saying nuh-uh. I used your own graphs to demonstrate what you laughed about - engines are designed with a viscosity in mind.

I've showed many times over why it's wrong ... you just can't understand it. It's really obvious you don't.

I answered the big question many people have, including me. Is too thick bad? Yes. It potentially decreases wear over time due to increased risk of metal-metal contact as a result of film breakdown.

You go read a book.
https://www.researchgate.net/public...ress_Fluids_with_Pressure-Dependent_Viscosity

Again, not an issue for ICE. Even guys who run super long OCIs with an oil that's up to it don't show major degradation from "bearing squeeze". So the bottom line is that even though journal bearings do "squeeze" the oil, it's not enough to matter. Another one of you grasping on something out of context wrt to an ICE. Context really matters in these discussions.

Any thing from xW-20 to xW-50 can be used in modern ICE .. even in your Rouge. Do you think those Nissan engieers are wrong, lol. And going up a grade from xW-20 is beneficial for the reasons shown.

 

[siriusc1024]

You can't say whether it's an issue or not. You have no idea because you hadn't heard about dynamic loading until a few hours ago. You actually thought dynamic loading meant changing rpms, ok? Give it some time and study.

Nissan says that because thicker oils at higher temps behave like the lower viscosity oils at regular temps. Not a hard concept. They aren't saying carte blanche run 20w-50 in the 0w-20 engine. They also say run 0w-20 or warranty is void. Either way what Nissan says is irrelevant to the dynamic loading discussion.

 

[ZeeOSix]

Let me give you the context. Wear over time. Transient conditions of quick metal-metal contact adding up. 150k instead of 275k. Not catastrophic failure. When film breaks down, additives like molybdenum and zddp take over.

Thicker oil doesn't cause that ... you've now latched on to your own self made-up misconception, lol. Just like all the data and tech info shows over and over, thinner oil results in more wear due to less MOFT. Way back in post 123 shows the data from a sophisticated SWRI test. Are you just trolling, or are you really not able to grasp this stuff?

 

[siriusc1024]

Thinner oils than the bearing design can support result in more wear*

I'm not trolling, so I'm going to stop so they don't lock the thread. You're making it personal for no reason. I'll work with data, though. I'll discuss. I'm not doing what you're wanting to do.

 

[ZeeOSix]

You can't say whether it's an issue or not. You have no idea because you hadn't heard about dynamic loading until a few hours ago. You actually thought dynamic loading meant changing rpms, ok? Give it some time and study.

Nissan says that because thicker oils at higher temps behave like the lower viscosity oils at regular temps. Not a hard concept. They aren't saying carte blanche run 20w-50 in the 0w-20 engine. They also say run 0w-20 or warranty is void. Either way irrelevant to the dynamic loading situation.

I didn't quite get how you wrote about it initially, so responded to what I though you meant. Yes, I know about dynamic loading ... even showed the 4-stroke engine cycle showing how the MOFT chages with the engine strokes. The MOFT can go to zero due to a low viscosity under dynamic loading where the MOFT is minimum, and of course with something LSPI it would be even worse. Thinner oil and less MOFT isn't going to protect bearings from dynamic loading better than thicker oil. Show a study where that was actually proven with testing on ICE. If it was going on to the point of causing MOFT to go to zero when running thicker oil, the whole world would know about it. I can hear it now: "Hey, I'm going to use some 0W-8 to protect my engine better from LSPI and high rod loads".

Why do you think journal bearings show more wear on the top side when low viscosity oil causes the MOFT to go to zero. But the bearing is better protected from top side wear when the oil is thicker and the MOFT is more? If you used xW-20 in a high HP engine in track use, based on your "dynamic loading" misconception, the the bearing should have more wear than if 0W-20 was used on the track. Guess all those engineers so spec thicker oil for high HP engines and track use just don't understand "dynamic loading" and should be going with the thinner oil instead, lol.

And I guess those GM engineers just caused more bearing and engine damage by going to 0W-40 as part of that engine recall.

 

[ZeeOSix]

Thinner oils than the bearing design can support result in more wear*

Like said many times ... too thin of an oil in a large clearance bearing is bad, that's what your statement would describe. It would result in low MOFT and have the most potential to cause more wear. But, all bearings in the right clearance range build more MOFT with thicker oil, across the board. The amount of MOFT increase from viscosity varies depending on other factors, but the bottom line is they will all have more MOFT with more viscosity when all the other factors are held constant. That's a simple aspect of journal bearings you just can't seem to understand. The SubsTech website will show you all of that, and why that's the case.

I'm not trolling, so I'm going to stop so they don't lock the thread. You're making it personal for no reason. I'll work with data, though. I'll discuss. I'm not doing what you're wanting to do.

If you're not trolling, then why can't you grasp some of this basic stuff. I mean you go dig up some out of context stuff to try and prove that thinner oil protects moving parts better. It just doesn't, no matter what you try to come up with and twist around. I give you this info, and you can go verify it too, but you just keep trying to twist everything up to convince yourself that thicker oil doesn't do anything beneficial, and even claim it's going to cause damage. I call that trolling, especially since it goes on in circles for days. If it's not trolling, then what is it besides not able to comprehend the way journal bearing work. Instead of going down rabbit holes trying to find proof that less MOFT gives more protection, go read up on how journal bearings actually work. Then you might get the whole picture.

Oh, I'm sure it's going to get locked ... just wait.

 

[ZeeOSix]

This is an issue of hydrodynamic delay.

To illustrate, here's QS Synthetic 0w-20 (8.33 cst @ 100C) and Valvoline VR1 20w-50 (20 cSt @ 100C)

Had to comment on these graphs after looking at them closer. From what I'm seeing, it takes MORE squeeze film pressure to obtain the same resulting clearance lines for the thicker oil vs the thinner oil. Look at the yellow line (1.0 mils of clearance) and the y-axis squeeze pressure levels. It takes much more squeeze pressure from 0 to 5 ms to get the clearance down to 1.0 mils for the thicker oil. So that tells me the thicker oil is less sensitive to, and retains more clearance with the same applied film squeeze pressure over the same time period compared to the thinner oil. Kind of opposite of the claim that thicker oil is "worse".

You claimed in post 363: "Too thick oil can result in metal-metal contact because the hydrodynamic wedge is too slow to adapt to the transient."

Those graphs say that's not true, because the thicker oil needs much more squeeze pressure to get to the 1.0 mils clearance over the 5 ms time period. If the same squeeze pressure that was put on the thinner oil (it's less than what was needed on the thicker oil) was put on the thicker oil over the same 5 ms time period, the clearance would end up being larger than 1.0 mils for the thicker oil. Or if the higher squeeze pressure used on the thicker oil was put on the thinner oil, then the thinner oil would have less clearance. So the thicker oil is less sensitive to squeeze pressure. Therefore, thicker oil would help protect journal bearings from dynamic loading.

 

[siriusc1024]

Had to comment on these graphs after looking at them closer. From what I'm seeing, it takes MORE squeeze film pressure to obtain the same resulting clearance lines for the thicker oil vs the thinner oil. Look at the yellow line (1.0 mils of clearance) and the y-axis squeeze pressure levels. It takes much more squeeze pressure from 0 to 5 ms to get the clearance down to 1.0 mils for the thicker oil. So that tells me the thicker oil is less sensitive to, and retains more clearance with the same applied film squeeze pressure over the same time period compared to the thinner oil. Kind of opposite of the claim that thicker oil is "worse".

Very good question. I got hung up on that, too. Yes that's correct. More pressure with the higher viscosity oil.

That axis is squeeze film pressure. It's resistance to flow as oil redistributes along the surfaces. It's not bearing support pressure.

Consider pressure and flow. Flow in a dynamic situation where a transient occurs. One geometry to another over a very short time. More pressure means more resistance to oil film redistribution (flow to the new state).

Take an already loaded bearing with established oil circulation and picture that state and what the oil wedge looks like. Now do the same for a higher load. Those two static concepts. Now introduce the time component to make it dynamic.

Squeeze pressure is resistance to flow to the new configuration.

If you're thinking that a higher viscosity fluid will support a changing load better, as I did, turns out that's partially correct. It's partially correct because as the force vector changes magnitude, the pressure field changes. It's not point pressure, it's a distribution. This is why the hydrodynamic wedge takes a different shape for different loads.

In this case, higher squeeze pressure means more lag to geometry reconfiguration - suboptimal lubrication. That correlates to both viscosity and clearance. With enough differential, the shaft may move into the bearing before the oil wedge is established to counteract the force!

For what it's worth, this dynamic concept doesn't negate the data you've supplied about film strength. Please don't take it that way. Many times I agreed with you, and you can go back through to confirm.

What I'm saying is that in a transient condition you have to apply dynamic terms. The supporting oil wedge will change shape as the force applied changes. It needs to change shape fast if the load changes fast. Those graphs show that shape can change faster for bigger clearances and thinner oil - both being less resistant to flow, hence lower (squeeze) pressure.

 

[Sienna dude]

"Thickies" need to realize that the Toyota 2.5L that takes 0w16 also keeps the oil temperature between 130 and 170 degrees 90% of the times. It achives that through a combination of oil cooler and the engine shutting off. It is very rare to see the engine on at idle.
I don't see a difference between a Tacoma with 0w20 at 200 degrees and a Camry with 0w16 at 170 degrees. A Camry having 0w16 at 220 degrees will be a problem but that will never happen, it just won't.

 

[ChrisD46]

If you think the ESP will provide better protection and oil pressure than Mobil 1 0w-40 FS then I might be willing to try it. I already commented on my experience with FS in a previous post. I honestly think M1 oils start out great but wear down quickly. I think the base stock sucks and they compensate with additives. That's just my opinion.

Right now I use QS Synthetic 5w-30 in the LS, QS Synthetic 0w-20 in the Rogue. 5k OCI on both. M1 filters.

As far as cleanliness with Dex lemme show ya. I just walked out and snapped this for you. This is my head bolt. I put a dash on the head bolts with permanent marker for degree torque. Rocker on the left (hint of bronze if you look closely by the snap ring). Bright aluminum casting in the head. I did the head swap 80k ago.


View attachment 280687

With the Rogue I'll confess that I have put 5w-30 in it once. Only once. Idea was to get better protection. See, I've already had this thick vs thin discussion with myself. The reasoning is that Nissan not only recommends but requires 0w-20 in that engine. I've already expressed how important it is to make consideration for the engine architecture when deviating from spec. I can't find enough information to make a good informed decision. Especially, now that I know about the existence of piston ring coatings commonly found in mpg-focused engines, I'm leery of going thicker. I'll stick to the spec.

PP 5W30 is a thin for grade 30 weight synthetic oil that may be considered for those stepping up from a 20 weight oil .

 

[chris719]

"Thickies" need to realize that the Toyota 2.5L that takes 0w16 also keeps the oil temperature between 130 and 170 degrees 90% of the times. It achives that through a combination of oil cooler and the engine shutting off. It is very rare to see the engine on at idle.
I don't see a difference between a Tacoma with 0w20 at 200 degrees and a Camry with 0w16 at 170 degrees. A Camry having 0w16 at 220 degrees will be a problem but that will never happen, it just won't.

I highly doubt this is true. BMW is shipping 382 hp 3.0L cars that run at 230 all the time for maximum efficiency and on 0W-12 now.

 

[ZeeOSix]

If you're thinking that a higher viscosity fluid will support a changing load better, as I did, turns out that's partially correct. It's partially correct because as the force vector changes magnitude, the pressure field changes. It's not point pressure, it's a distribution. This is why the hydrodynamic wedge takes a different shape for different loads.

In this case, higher squeeze pressure means more lag to geometry reconfiguration - suboptimal lubrication. That correlates to both viscosity and clearance. With enough differential, the shaft may move into the bearing before the oil wedge is established to counteract the force!

For what it's worth, this dynamic concept doesn't negate the data you've supplied about film strength. Please don't take it that way. Many times I agreed with you, and you can go back through to confirm.

What I'm saying is that in a transient condition you have to apply dynamic terms. The supporting oil wedge will change shape as the force applied changes. It needs to change shape fast if the load changes fast. Those graphs show that shape can change faster for bigger clearances and thinner oil - both being less resistant to flow, hence lower (squeeze) pressure.

Re: The statement in bold. If the squeeze film pressure is higher and means more "lag time" to reconfigure, then that means the thicker oil in the previous graph shows it takes more squeeze film pressure over that 5 ms time period to achieve the 1.0 mils clearance, which is what I was getting at before. So thicker oil takes more squeeze film pressure to react. That means it's going to resist dynamic shock loads better and protect the bearing better on the power stroke. The thicker oil will maintain it's better MOFT longer during the shock loading. I guarantee you that if you ran xW-20 in a super high HP boosted engine, the top area of the rod bearings are going to last a lot shorter than if xW-50 was used.


I'm going to go the more direct route here, and just find references that say thicker oil is better for shock loads. And that info is out there, so it corresponds with what I said above.

Source: https://www.stle.org/files/TLTArchives/2023/10_October/Lubrication_Fundamentals.aspx

"Oil viscosity requirements for journal bearings vary from as low as 12 centistokes (cSt) to as high as 350 cSt at operating temperature, all depending on the journal speed, or revolutions per minute (rpm), and whether the load is steady and moderate. If the bearing is heavily loaded or is expected to experience shock loads, another speed versus viscosity curve is used to determine an ideal, slightly higher viscosity than with the steady and moderate load."

Source: https://precisionlubrication.com/articles/extend-bearing-life-with-lubricant

"For very slow-moving and heavily loaded element bearings, it is appropriate to select even higher-viscosity oils and greases and incorporate solid-film agents for enhanced protection against shock loading and loss of EHD condition."

Also ... the bottom line is that thicker oil in a journal bearing will provide additional shock load protection, so another benefit. Just run some thin oil in a very highly boosted engine and find out how much abuse the journal bearings will see on the top side.

 

[ZeeOSix]

"Thickies" need to realize that the Toyota 2.5L that takes 0w16 also keeps the oil temperature between 130 and 170 degrees 90% of the times. It achives that through a combination of oil cooler and the engine shutting off. It is very rare to see the engine on at idle.

Of course one trick to use thinner oil is to control the max temperature better. Same goes with track cars, where the hard core track guys add more or better oil coolers.

 

[siriusc1024]

Re: The statement in bold. If the squeeze film pressure is higher and means more "lag time" to reconfigure, then that means the thicker oil in the previous graph shows it takes more squeeze film pressure over that 5 ms time period to achieve the 1.0 mils clearance, which is what I was getting at before. So thicker oil takes more squeeze film pressure to react. That means it's going to resist dynamic shock loads better and protect the bearing better on the power stroke. The thicker oil will maintain it's better MOFT longer during the shock loading. I guarantee you that if you ran xW-20 in a super high HP boosted engine, the top area of the rod bearings are going to last a lot shorter than if xW-50 was used.


I'm going to go the more direct route here, and just find references that say thicker oil is better for shock loads. And that info is out there, so it corresponds with what I said above.

Source: https://www.stle.org/files/TLTArchives/2023/10_October/Lubrication_Fundamentals.aspx

"Oil viscosity requirements for journal bearings vary from as low as 12 centistokes (cSt) to as high as 350 cSt at operating temperature, all depending on the journal speed, or revolutions per minute (rpm), and whether the load is steady and moderate. If the bearing is heavily loaded or is expected to experience shock loads, another speed versus viscosity curve is used to determine an ideal, slightly higher viscosity than with the steady and moderate load."

Source: https://precisionlubrication.com/articles/extend-bearing-life-with-lubricant

"For very slow-moving and heavily loaded element bearings, it is appropriate to select even higher-viscosity oils and greases and incorporate solid-film agents for enhanced protection against shock loading and loss of EHD condition."

Also ... the bottom line is that thicker oil in a journal bearing will provide additional shock load protection, so another benefit. Just run some thin oil in a very highly boosted engine and find out how much abuse the journal bearings will see on the top side.

View attachment 281079

No. The bearing is supported by the oil wedge. That way of looking at it only works if there is no high pressure gradient of oil film (no circulation) and relying on viscosity alone.

You're thinking about it like squeezing something out from between two surfaces. That's not what's going on. Again, the circulation and wedge formation.

The oil wedge has to be developed. As conditions change development changes.

 

[ZeeOSix]

No. The bearing is supported by the oil wedge. That way of looking at it only works if there is no high pressure gradient of oil film (no circulation) and relying on viscosity alone.

The MOFT oil wedge is where the pressure gradient lives as shown in the previous bearing shot you posted. There is a high pressure gradient of oil in the MOFT, the pressure profile is shown in that bearing diagram. There is always oil circulation going on in the bearing, due to the oil wedge formation from the viscosity and bearing rotation, and there is also some natural side leakage out the sides of the bearing. What leaks out is replenished by the oil supply to the bearing. Don't know what you're trying to say here. Guess you still haven't tried to educate yourself on how journal bearings acually work.

You're thinking about it like squeezing something out from between two surfaces. That's not what's going on. Again, the circulation and wedge formation.

When the bearing gets a shock load, as when the rod experiences combustion pressure and load. the rod load tries to squeeze the oil out of the MOFT area where all the high film pressure is at that time. That's why the MOFT occurs on the top side of the bearing on the power stroke. As shown, it takes more pressure to make thicker oil squeeze out, therefore thicker oil is more resistant to shock loading. The thinner the oil and lower the MOFT is, the more apt the MOFT goes to zero under a shock load. This is probably the main reason rod bearings show way more wear on the top side on the rods big ends. BTW, when data is shown for rod bearings, and the MOFT is shown, that's the film thickness due to the shock load in the rod.

The oil wedge has to be developed. As conditions change development changes.

What are you talking about? ... "has to be developed". The oil wedge is always there as long as the bearing is rotating. What do you think causes the supporting oil wedge to actually "develop"? Sure the oil wedge where the MOFT lives and changes due to many factors as discussed for days in this thread, yet it doesn't seem to sink in, lol.