I think this was previously believe to be true but experimental data has called into question. I'm looking for the paper I saw to this effect.
Confessions of a Recovering Thickie
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I think this was previously believe to be true but experimental data has called into question. I'm looking for the paper I saw to this effect.
I am simply stating that I am glad some form of logic is being applied other than opinions based on emotion or feelings.
It does sound like logic, but it’s the wrong tool for the job. Blackstone themselves claim statistically there is no wear difference between brands. They do however claim to see wear differences in viscosity and usage type(like severe service). Also consider a UOA only sees particles of certain sizes. Not sure it is accurate of total wear.
A Blackstone type UOA can only see particles 5u and smaller. So it takes a lot of wear difference (ie, a lot more particles 5u and smaller) to see the effect in the UOA (ie wear has to get into the "Advanced" wear realm to see a good uptick), so it's pretty insensitive until a lot of wear starts to happen. Plus the wear trend and possible red flags can only really be seen if routine UOAs are done. When there's a distinct deviation from the wear treand history, then it could show an issue is going on.
If you look at the info in Figures 2 & 3 in the link below, it shows that if the bearing clearance is too tight then the the MOFT drops off drastically, which means it would take less load to make the MOFT go to zero. A bearing that maintains higher MOFT with the load is the bearing that has more load capability. The load capability limit is when the MOFT goes to zero, so this is just another reason to have more MOFT in the bearing than not. Going up in viscosity gives more MOFT, which would mean it also gives the bearing more load carrying capacity. More MOFT in the bearing is what gives them more wear protection headroom.
Note that at any given bearing RPM, the MOFT is pretty constant bewtween a clearance of 0.001 and 0.002 inch. Also, MOFT goes up some as clearance increases depending on the bearing rotational speed. The data is based on a 2 inch journal, so 0.001 inch clearance on that journal is 0.0005 in/in of journal dia, and the 0.002 clearance is the nominal 0.001 in/in of journal dia general rule used forever. That range of clearance is basically what engine manufactuers are shooting for (those basic clearances have been used for decades), and is right in the range of the Ford Coyote (0.0005 in/in for main bearings and 0.001 in/in for rod bearings) as I posted the factory sevice manual specs someplace recently.
This websit is a treasure trove of journal bearing info, and is the website of King Engine Bearings, who are well known for high performace journal bearings.
https://www.substech.com/dokuwiki/doku.php?id=oil_clearance_and_engine_bearings
Here's another graph from SubsTech (King Bearings) showing the bearing clearance sweet spot is in the 0.001 to 0.002 inch range when considering the bearing RPM range. At lower speeds, the MOFT drops off after 0.002 inch. This is why bearing clearances have been in this range for about forever, because the engineers figured out a long time ago this is where they need to be for optimum MOFT for any given viscosity. Then there's the viscosity factor, which will give more MOFT with more viscosity. The whole goal with journal bearings is to achieve a more than adequate MOFT considering all the factors that influence the supporting oil film wedge in the bearing. You don't want to be running on the ragged edge of zero MOFT.
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Yes I've seen references to where too thick can result in lubricant breakdown. I spoke about this, but couldn't detail.
Here's something interesting pertaining to viscosity, hydrodynamics, and clearances.
"Despite all the anomalies, almost all of these correlations estimate the viscosity as an exponential function of pressure. This manifests the possibility of dramatic increase in the viscosity of lubricants with respect to rise in pressure. Thereby, under piezo-viscous situation, increase in contact pressure may result in thickening of the lubricating fluid. Overall, this means, an incremental pressure rise may at some point be detrimental to a lubricant’s performance. Intuitively, thickening of lubricant may seize the lubricant’s flow and leading to a failure of lubrication, in other words, by lubricant fracture!"
https://www.tribonet.org/wiki/pressure-viscosity-coefficient-and-characteristics-of-lubricants/
They're talking about pressure here. I would think tighter clearances on a bearing would mean more distribution of force, decreasing localized pressure.
Still, it is a phenomenon that the flow can breakdown at a higher viscosity. Just picturing in my mind it makes sense that in order for the lubricant to maintain rotational flow in a tighter area it would need to be thinner.
I don't think going up a grade would be too consequential. In the example of 20w-50 listed where 0w-20 is preferred for the Rogue, I believe 20w-50 would cause inadequate lubrication unless heated up enough to bring viscosity down.
I'll keep looking in the interest of finding out more about how lubricants work.
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Yes, it is good that logic is being applied even if the discussion gets heated. I'm fine with being proven wrong because it means that questions I had have been answered. Plus, if anyone had the same thoughts now they can see the answers, too. It's a good perspective to see both sides of an issue displayed in detail. This furthers discussion and understanding.
Not sure why some go for the personal attacks. It doesn't further discussion and understanding because some have questions, and they may be hesitant to ask an acerbic group.
I'm no fan of 0w5.... Never have and never will use it.
Your ass sensor/measurement is something, as far as I am concerned.
0w20 in an FJ Cruiser is very, very different than a stout 10w30 and the 10w30 reigns supreme, as long as you aren't starting the vehicle in negative 30 temps.
Never will I buy in to the "water thin" oils.... and I also won't use the wide spans, like 5w40 or 5w50 or 0w30. Those dudes shear out way too quickly.
Give me a very robust 10w30 and my engine is a very, very happy camper.... or a 15w40 for the heavier applications.
Your ass sensor/measurement is something, as far as I am concerned.
0w20 in an FJ Cruiser is very, very different than a stout 10w30 and the 10w30 reigns supreme, as long as you aren't starting the vehicle in negative 30 temps.
Never will I buy in to the "water thin" oils.... and I also won't use the wide spans, like 5w40 or 5w50 or 0w30. Those dudes shear out way too quickly.
Give me a very robust 10w30 and my engine is a very, very happy camper.... or a 15w40 for the heavier applications.
Hohn was talking about bearing clearance vs bearing load capacity, not "lubricant breakdown".
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Well I am. That's for me to support, so I'm not disputing anything right now. I think 20w-50 will result in reduced engine life on the Rogue. I can conceptualize why. Now I have to find more info if it's true or not. That article might be a lead.
You're shooting in the dark. How many UOAs have you seen where the used oil KV100 actually gets higher? Very few, and the ones that do is not caused by the oil getting pressed into the high pressure wedge inside the journal bearings.
Higher KV100 multi-viscosity with a larger spread between the W grade and KV100 grade can permanently shear more than one with less of a spread between the W grade and KV100 grade. That permanent shear thins down the oil, and why almost all UOAs will show a lower KV100 than the new oil did. Some VIIs can permanently shear pretty good depending on what VIIs are used, and the engine it's used in (ie, like engines with lots of cam-chains and gears in the valve train).
Those Nissan engines that can use anything from xW-20 to xW-50 per the OM must be something special ... not really. Any engine can run that range of viscosity and no "bad things" are going to happen if it's higher viscosity than xW-20.
Keep looking, and also should study up on how journal bearings really work. Lots of it has already been covered in this thread, but there's always room for more. You seem to still be trying to justify xW-20, even though the same engine can do xW-50 per the Nissan engineers.
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Pretty sure what they are saying is thickening of a lubricant means selecting a thicker lubricant.
And here's another reason I suspect too high viscosity can result in harm. Notice how the MOFT trends downward as clearance decreases? Can anyone explain that?
I'm fine with -30 in the Rogue. Not -50. There is a point where thick becomes too thick. At least, that's what I'm exploring.
Looks like that 2 thou you were talking about is a sweet spot. What if a bearing is running with .001? Look at the graph.
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High KV100 isn't going to cause harm - you think Nissan would show in the OM that a 20W-50 could be used if it "caused damage"?
That graph has nothing to do with oil thickening - you're not understanding the graph. The oil viscosity was a constant in that graph, and the purpose of the graph is to show how the bearing clearance effects the MOFT with a constant oil viscosity. It shows that if the bearing clearance is too large than the MOFT decreases. This happens with any viscosity as the bearing clearance increases - even worse with thinner oil. The worse combination is larger bearing clearance with thin oil. The lower the viscosity the more the MOFT drops off as bearing clearance increases. This is why the journal bearings ideal clearance is around 0.001 to 0.003 inch in that graph, where the curve is near max and pretty flat. Go back and re-read those posts, and go to that SubsTech website I linked earlier if you want to study journal bearings and how they work and react to viscosity, speed and load. It's a treasure chest of jouirnal bearing information.
The bottom line is you want more MOFT than not in journal bearings because that is the only thing keeping them in full hydrodynamic lubrication, and not prematurely wearing out because the MOFT is too small or if it goes to zero often. This is why going up at least a grade if the spec is xW-20 or less is benificial to give some added protection.
Well sure, going with a xW-30 over a xW-20 is going to give some more MOFT, which is what you want. xW-50 would give some more, but unless you're going to tack the Rouge then xW-30 is good for street driving if you want some wear protection headroom. Who doesn't like headroom in things where you can achieve headroom?
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I agree with you totally about MOFT. I'm just going to say this one thing then get to looking. Might find it might not. I think it's possible too high viscosity can decrease MOFT due to flow breakdown as a function bearing clearance. I think bearing clearance and viscosity have an inverse non-linear relationship (2 grades difference more than double the effect of 1 grade).High KV100 isn't going to cause harm - you think Nissan would show in the OM that a 20W-50 could be used if it "caused damage"? You're not understanding the graph. It shows that if the bearing clearance is too large than the MOFT decreases. This happens with any viscosity as the bearing clearance increases - even worse with thinner oil. The worse combination is larger bearing clearance with thin oil. The lower the viscosity the more the MOFT drops off as bearing clearance increases. This is why the journal bearings ideal clearance is around 0.001 to 0.003 inch in that graph, where the curve is near max and pretty flat. Go back and re-read those posts. and go to that SubsTech website is you want to study journal bearings and how they work and react to viscostiy, speed and load.
The bottom line is you want more MOFT than not in journal bearings because that is the only thing keeping them in full hydrodynamic lubrication, and not wearing out because the MOFT is too small of goes to zero often. This is why going up at least a grade is benificial to give some added protection.
Well sure, going with a xW-30 over a xW-20 is going to give some more MOFT, which is what you want. xW-50 would give some more, but unless you're going to tack the Rouge then xW-30 is good for street driving if you wand some wear protection headroom. Who doesn't like headroom in things where you can achieve headroom?
Go to that SubsTech website (King Bearing - they are experts in aftermarket bearings) that I linked in an earlier post, and you can read about journal bearings for days, lol. Of all the research I've done on journal bearings and oil, I have never came across that claim in your post.
This is something to consider, and you will learn with study. A tighter bearing clearance increases the shear rate of the oil in the MOFT, and that can "degrade" the oil due to permanent shear which will thin a multi-viscosity oil. Tight bearings also cause the oil temperature inside the bearing to increase more due to that higher shear rate. That's why those bearing temp rise curves skyrocket as the bearing clearance gets too tight. The fastest way to smoke a bearing is to have the clearance too tight. But again, the ideal clearance is pretty much 0.0005 in/in of journal dia for main bearings, and 0.001 in/in of journal dia for rod bearings. Engine engineers figured that's the ideal bearing cleance decades ago, and that's prettty much what every mass produced road vehicle is running for bearing clearances.
The 20W grade would be more concerning if used in too cold ambient temps than the KV100 50 grade at operating temperature. There are literally multi-millions of vehicles with similar bearing clearances using xW-40 and xW-50 oils all over the world. If it was damaging, that wouldn't be going on, nor would the Nissan engineers show it as an option in the OM in the very engine that's in your Rouge. It's not a very big logic leap to see.
Even this guy finally has agreed that thicker oil provides more protection. He had another video where he was praising thinner oil viscosities, this GM story possibly made him re-think
Engineering Explained
Engineering Explained
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Unbelievable. I just finished that video and was about to link it. Unbelievable as in that's not the message of the video. The takeaway from the video is that thinner oils, where specified, do not cause more wear.
He speaks about the L87 GM recall. It's noted that in engines that are warrantied the new ones are spec'd 0w-20. GM is so confident in this that they extend the warranty 10 yrs/150000 miles.
Look at his own flagged comment:
"*Important Note!* I asked a GM powertrain engineer directly about this, who spends his life living and breathing modern performance engines (and specifically small block V8s). Regarding the L87 engine discussed in this video, I asked directly if today's modern, thinner engine oils are too thin for enabling reliability and cause concern of additional engine wear. His answer was a very concise "no." Testing validates this. I think if you watch this video fully (which is quite information dense!), you'll come to understand why. The blame does not lie on the engine oil, as the video breaks down in great detail. Did a lot of research for this one - hope you enjoy it!!"
Importantly, he also calls out the CAFE compliance conspiracy nonsense and explains why the notion of low viscosity just to meet mpg doesn't hold up to scrutiny.
Un freaking believable dude. And people accuse me of cherry picking.
I recommend people watch for themselves.
Yes, he said that thinner oil in many cases provides enough protection.
But then he said “what if you use thicker oil when its not necessary”. His only response was it will generate more heat and worse MPG. He did not mention any other side effects. Just said its not necessary because you already getting needed protection
Thicker oil is just an insurance margin in case your viscosity drops due to fuel dilution or you like to drive hard, or your OEM messed up (like GM). And I did watch video fully. Zero reasons were provided why higher viscosity can cause issues. Higher heat and lower MPG are not good reasons. Higher viscosity provides safety margin in case things go south
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