Are thinner oils about fuel economy or tighter engines?

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...To elucidate further, I invite you to revisit my initial statement where all the pertinent assumptions were provided. Thus, it is evident that our discourse remains grounded in a framework of average assumptions :) but in the middle was this -
I have seen every statement you have made and you have, it seems, been focused on one aspect of an oil's viscosity verses analine point and solvency without taking into account all of the factors involved in viscosity, both mathematical and material.
 
I've already discussed this; it relates to heat transfer and shows a slight improvement.
"It shows a slight improvement" ... please link the official test results of that.

You keep claiming there is an advantage to a hot thinner grade oil "flowing down" due to gravity compared to a hot thicker oil - both at 100C. Explain how that relates to a change in heat transfer of the oil as it "flow down", or any other claimed lubricating advantage. There is zero realistic advantage of a thinner hot oil except maybe a slight increase in fuel economy with the risk of increased engine wear.

I would like to reiterate my point once again. I shared the video in response to your mention of cold-oil-related aspects. My intention was simply to provide a visual representation of the actual scenario, purely for amusement purposes. I have no agenda to persuade or dissuade you on any matter. If you happen to have a different perspective and wish to engage in a discussion, please feel free to do so. However, I would like to clarify that my intent is to share my thoughts rather than engage in weird arguments :)
The video was "entertaining", but it also supports my views of cold oil flow being proper and not detrimental if the correct "W" grade is used in cold start-up environments.

Seems you are sharing your thoughts along with your own "weird arguments" ... maybe it's all just for (trolling?) type of "entertainment", which seems to be the explanation of the latest "thoughts". We are all sharing our thoughts, but some make more sense than others. ;)
 
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xactly what does that mean? The words are very pretty, but mean practically nothing. It seems to me that the essence of the discussion lies within the facts being discussed, not intermediate considerations.
When discussing the use of thinner or thicker oil, it is essential to consider the perspective of an average, which are based on average conditions. These considerations encompass the prevailing average formulations of thinner and thicker PCMOs available in the market.
 
When discussing the use of thinner or thicker oil, it is essential to consider the perspective of an average, which are based on average conditions. These considerations encompass the prevailing average formulations of thinner and thicker PCMOs available in the market.
More word salads and it's getting old.
 
I have seen every statement you have made and you have, it seems, been focused on one aspect of an oil's viscosity verses analine point and solvency without taking into account all of the factors involved in viscosity, both mathematical and material.
I was simply seeking valuable insights (one major and one minor option) for reducing viscosity, and I am pleased to have shared my findings :) Agree?
Have I, at any point, criticized the notion of increased viscosity? It is important to note that my original post does not revolve around criticism but rather explores potential benefits, as reflected in my personal thoughts and perspectives.
 
The video was "entertaining", but it also supports my views of cold oil flow being proper and not detrimental if the correct "W" grade is used in cold start-up environments.
That's great to hear! :)
Moving on to the potential benefits of oil movement, it can be quite challenging to find scientific literature specifically focused on such aspects within the realm of internal combustion engines. While there are references available in amateur forums, scientific studies exploring the intricate dynamics of oil flow and the underlying heat equation in these layers might be relatively scarce. Determining the optimal viscosity requirements can be a complex matter, as the chemical properties of modern low-viscosity oils are quite promising. It's possible that their viscosity might be sufficient, but as mentioned before, I am merely reiterating this point.
 
I've already discussed this; it relates to heat transfer and shows a slight improvement.
To add ... keep in mind that higher viscosity oil has a higher heat capacity per volume, so it takes more absorbed heat to raise it's temperature. The same volume of thinner oil will heat up more with the same amount of absorbed heat. In practicality, it still wouldn't make any real amount of difference to be concerned about.
 
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I was simply seeking valuable insights (one major and one minor option) for reducing viscosity, and I am pleased to have shared my findings :) Agree?
Have I, at any point, criticized the notion of increased viscosity? It is important to note that my original post does not revolve around criticism but rather explores potential benefits, as reflected in my personal thoughts and perspectives.
"Now, let's explore the significance of viscosity reduction and its impact on engine oils.
By using oils with lower viscosity, we can achieve a few benefits. Firstly, the oil flows down more easily, which is a small but positive advantage. Secondly, and more importantly, lower viscosity oils have greater solvent capacity."

To review, we were discussing clearances, oil flow, and molecular sizing.

But in your statement above ('the oil flows down more easily'), you seem to have ignored that oil is under pressure by a PD pump. Calculate the pressure due to mgh gravity flow in a 1/2" (12.5mm) pipe and then calculate oil flow due to a PD pump providing 50 psi of pressure and you will see that a pressurized lubrication system trumps any gravity flow system by a magnitude.

As I mentioned in a previous post, the major advantages to modern low viscosity oils are mpg and less engine HP heating the oil, all of which are very small fractions to be gained in any scenario.

I don't see solvent potential as providing much of a gain for the engine which needs to see a majority of hydrodynamic lubrication in order to minimize wear.
 
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To add ... keep in mind that higher viscosity oil has a higher heat capacity, so it takes more absorbed heat to raise it's temperature. Thinner oil will heat up more with the same amount of absorbed heat.

I must admit :) that my level of interest in this particular topic was not extensive. Therefore, I only came across a 2 pictures that provided a glimpse into the dynamics associated with it.

he1.webp
he2.webp
 
you seem to have ignored that oil is under pressure by a PD pump

No, I have already engaged in a discussion regarding this matter with ZeeOSix. My focus was solely on the movement of oil as it exits channels and gaps, particularly emphasizing the self-draining/self-flow nature in areas where it becomes feasible after the exit.
 
But in your statement above ('the oil flows down more easily'), you seem to have ignored that oil is under pressure by a PD pump. Calculate the pressure due to mgh gravity flow in a pipe and then calculate oil flow due to a PD pump and you will see that a pressurized lubrication system trumps any gravity flow system by a magnitude.
I think he's talking about the oil that is only driven by gravity, not anything in the pressurized (PD pump force fed) areas of the oiling system. Any oil viscosity from 0W-8 to xW-60 that's at 100C will be "flowing down" due gravity to the sump very quickly, and any difference has zero significance.
 
You could have surprised me.

I'm sorry, I didn't attempt to provide an exact answer in this discussion. The limit of sufficient viscosity for modern internal combustion engines (PC) and their compatibility with modern PCMO is not definitively known :) (2 cP ? who knows..)
 
No, I have already engaged in a discussion regarding this matter with ZeeOSix. My focus was solely on the movement of oil as it exits channels and gaps, particularly emphasizing the self-draining/self-flow nature in areas where it becomes feasible after the exit.
I'll ask again. Please give an example how xW-20 at 100C "flowing down by gravity" inside an engine will improve or enhance lubrication compared to a xW-50 at 100C "flowing down by gravity".

What do you think the actual time difference would be for 1 quart of xW-20 at 100C to flow back from the heads to the sump would be compared to a xW-50 at 100C? I say it's so small that it's just hair splitting, and makes absolutely zero difference in lubrication effectiveness - no practical advantage of one over the other.
 
I'll ask again. Please give an example how xW-20 at 100C "flowing down by gravity" inside an engine will improve or enhance lubrication compared to a xW-50 at 100C "flowing down by gravity".

What do you think the actual time difference would be for 1 quart of xW-20 at 100C to flow back from the heads to the sump would be compared to a xW-50 at 100C? I say it's so small that it's just hair splitting, and makes absolutely zero difference in lubrication effectiveness - no practical advantage of one over the other.

The flow behavior of the oil is dictated by the characteristics of the specific locations and clearances involved, including the dimensions of the channels and other mechanical factors.

In seconds, but narrow channel -

sae.webp
 
The flow behavior of the oil is dictated by the characteristics of the specific locations and clearances involved, including the dimensions of the channels and other mechanical factors.

In seconds, but narrow channel -

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There really are not "narrow channels" in an engine for the oil in the heads, etc to drain back to the sump, unless the engine was designed by a complete amateur.

Do realize that some engines (like some Subarus) have oil pumps that flow near 15 GPM at high RPM. If the sump holds 5 quarts, that would mean the entire sump is circulated 12 times in one minute - that's one sump volume circulation every 5 seconds. If the oil didn't flow down fast enough the sump level would get too low and starve the oil pump of inlet oil. That doesn't happen if the oil is hot ... it "might" happen if the oil was super cold and thick like I mentioned before.

I want to see hot "flow down to the sump" test data in a real engine, not in a KV viscometer which as zero to do with how it flows down inside an engine.
 
There really are not "narrow channels" in an engine for the oil in the heads, etc to drain back to the sump, unless the engine was designed by a complete amateur. Do realize that some engines have oil pumps that flow near 15 GPM at ihigh RPM. If the sump holds 5 quarts, that would mean the entire sump is circulated every 12 seconds. If the oil didn't flow down fast enough the sump level would get too low and starve the oil pump of inlet oil. That doesn't happen if the oil is hot ... it "might" happen if the oil was super cold and thick like I mentioned before.

I want to see hot "flow down to the sump" test data in a real engine, not in a KV viscometer which as zero to do with how it flows down inside an engine.

I believe it is highly unlikely that such calculations exist, given the complexity of the system. Numerous factors come into play, such as drainage along the walls, mist formation (which, by the way, is influenced by thin/thick viscosity but can be affected by polymers), and various other intricacies. The intricate nature of this system makes it challenging to accurately assess all the points of runoff, the different layers involved, and the overall movement. Consequently, obtaining precise data of this nature is improbable. Nevertheless, it is reasonable to expect that the drainage performance may be notably improved by PCMO SAE16 vs SAE40 (e.g., average).
 
I'll ask again. Please give an example how xW-20 at 100C "flowing down by gravity" inside an engine will improve or enhance lubrication compared to a xW-50 at 100C "flowing down by gravity".

What do you think the actual time difference would be for 1 quart of xW-20 at 100C to flow back from the heads to the sump would be compared to a xW-50 at 100C? I say it's so small that it's just hair splitting, and makes absolutely zero difference in lubrication effectiveness - no practical advantage of one over the other.
Are you referring to Cylinder head drains, the small holes located right beside the valves, just opposite to the cylinder head mounting bolts? Their function of course is to allow oil to be recirculated to the sump to be reused by the engine.

@ArthurArgentum Why don't you both assume a size of say 1/2" or 12.5 mm and calculate the flow down rate using oil viscosities at the extreme ends of viscosity, say 7.0 cSt vs 19 cSt.?
 
Are you referring to Cylinder head drains, the small holes located right beside the valves, just opposite to the cylinder head mounting bolts? Their function of course is to allow oil to be recirculated to the sump to be reused by the engine.
Yes, any flow path, including holes in the heads, etc that allow oil to drain back to the sump. Any good engine designer isn't going to make those flow paths too flow restrictive, even for cold oil, and take a chance of not enough oil will drain back and keep the sump at a safe level.
 
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I believe it is highly unlikely that such calculations exist, given the complexity of the system. Numerous factors come into play, such as drainage along the walls, mist formation (which, by the way, is influenced by thin/thick viscosity but can be affected by polymers), and various other intricacies. The intricate nature of this system makes it challenging to accurately assess all the points of runoff, the different layers involved, and the overall movement. Consequently, obtaining precise data of this nature is improbable. Nevertheless, it is reasonable to expect that the drainage performance may be notably improved by PCMO SAE16 vs SAE40 (e.g., average).
It's a non-issue, and the difference between a xW-16 and xW-50 at 100C "flowing down by gravity" back to the sump is hair splitting. The "flow down" paths if designed well will allow oil to quickly drain back to the sump and keep the sump level at a safe level, even during extended high RPM runs. If it didn't, cars used on the track would be blowing up on a daily basis.

Edit - to add, there are many flow paths (if designed right) from the top end of an engine for the oil to flow back to the sump. Regardless of the oil viscosity when at operating temperature, the oil is going to flow quickly back to the sump. No magical enhancement to engine lubrication will be realized in this regard when using a thinner vs thicker viscosity grade.
 
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