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Sources of engine heat and effects of oil viscosity #4894394
10/12/18 01:41 AM
10/12/18 01:41 AM
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OilUzer Offline OP
OilUzer  Offline OP
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in general, what % of engine heat is generated by viscous shearing, combustion or friction? Anything else terminology wise? Is viscous shearing a component of friction which is causing the heat, and heating up the oil which is heating the block ...

I always thought that most of the engine heat is from combustion ... viscous shearing was mentioned in one the recent threads on this forum and made me wonder about the percentages.

my final question and as much as I enjoy it, grin2 it is not my intention to turn this into thick vs. thin discussion crzy shocked2 some will be assimilated eventually LOL
However, if you were NOT concerned about any other oil functions/qualities EXCEPT heat generation (viscous shearing? and friction) and heat transfer (e.g. away from the engine to oil cooler or the block), how does lower viscosity oil compare to higher viscosity oil? overall which oil will keep the engine cooler? I've read that thinner oil causes less heat but thicker oil will carry more heat (away) so I'm not sure about overall impact!

Re: Sources of engine heat and effects of oil viscosity [Re: OilUzer] #4894395
10/12/18 01:52 AM
10/12/18 01:52 AM
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Shannow Offline
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.

Ricardo Friction MEP.JPGMOFT Viscosity RPM.jpgbig end temperature.JPGheat flow in crankshaft.JPGheat flow in crankshaft 6000 rpm.JPGwarmup.JPGwarmup2.JPGcranking temperature increase.JPG

If you start on your own journey
And you find a path
...It's someone else's path.
Re: Sources of engine heat and effects of oil viscosity [Re: OilUzer] #4894398
10/12/18 02:05 AM
10/12/18 02:05 AM
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Shannow Offline
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Ultimately every bit of energy in an engine comes from the fuel (yes, even the energy in the battery), so ALL heat comes from combustion.


If you start on your own journey
And you find a path
...It's someone else's path.
Re: Sources of engine heat and effects of oil viscosity [Re: OilUzer] #4894399
10/12/18 02:07 AM
10/12/18 02:07 AM
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Shannow Offline
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Originally Posted by OilUzer
I've read that thinner oil causes less heat but thicker oil will carry more heat (away) so I'm not sure about overall impact!


Where have you read that thicker carries away more heat ?

Interested in sources...

Per heat transfer, a heavier oil should carry more heat per unit volume, but that's about it.


If you start on your own journey
And you find a path
...It's someone else's path.
Re: Sources of engine heat and effects of oil viscosity [Re: OilUzer] #4894400
10/12/18 02:14 AM
10/12/18 02:14 AM
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ZeeOSix Offline
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Dang Shannow ... your first post has all kinds of "scary" graphs and tables. wink

Re: Sources of engine heat and effects of oil viscosity [Re: ZeeOSix] #4894401
10/12/18 02:19 AM
10/12/18 02:19 AM
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Shannow Offline
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Originally Posted by ZeeOSix
Dang Shannow ... your first post has all kinds of "scary" graphs and tables. wink


Halloween is coming...wanted to get into practice before scary clown day.


Hang onto your breeches, as here's a paper as well...

https://www.researchgate.net/public...e_problem_causes_and_potential_solutions

I understand they reduce grown men to quivering messes.


If you start on your own journey
And you find a path
...It's someone else's path.
Re: Sources of engine heat and effects of oil viscosity [Re: OilUzer] #4894404
10/12/18 02:42 AM
10/12/18 02:42 AM
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OilUzer Offline OP
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Thank you! I will have to study the above charts and figure and see if I can come up with some numbers. I am assuming my questions may not have a simple yes/no or % answers.

Another question after seeing the above charts, assuming that less heat is generated with thinner oil at the beginning of the oil life cycle ... the engine may run cooler at first compared with thicker oil. However after several thousand miles, is it possible that thicker oil may "lubricate" better (friction wise) and produces less heat than a thinner oil of the same age? You see what I am getting at? Basically is it possible that thinner oil has advantage (heat generation wise) at the beginning and for a while (let's say few thousand miles) but when old(er), thicker oil will produce less heat? I am just trying to understand the science of it and this is not going to influence my choice of viscosity. Was trying to avoid thin vs. thick but looks like it's not possible grin2

Re: Sources of engine heat and effects of oil viscosity [Re: Shannow] #4894407
10/12/18 02:49 AM
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OilUzer Offline OP
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Originally Posted by Shannow
Ultimately every bit of energy in an engine comes from the fuel (yes, even the energy in the battery), so ALL heat comes from combustion.


I meant the heat generated by moving parts and friction (where oil comes into play) vs. the heat generated by combustion.

Re: Sources of engine heat and effects of oil viscosity [Re: OilUzer] #4894410
10/12/18 02:55 AM
10/12/18 02:55 AM
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Shannow Offline
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Dunno...there's only one poster in the thread so far who has used the "thick/thin" verbiage and multiple times...you say that you are avoiding that, then reference it, then state that it's unavoidable...why ?

You can look at the Stribeck curve, with and without friction modifier effects, and that will add understanding.

I've posted around BITOG (can't be arsed finding it) of my experiments with a type K thermocouple in the dipstick hole of my Briggs mower..5W20, and 25W60 as book ends...the increase in temperature was 100% due to the increase in viscosity, and clearly measurable...just didn't make an horrific knock on cold start like the 5W20 did at 30C.


If you start on your own journey
And you find a path
...It's someone else's path.
Re: Sources of engine heat and effects of oil viscosity [Re: Shannow] #4894415
10/12/18 03:00 AM
10/12/18 03:00 AM
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OilUzer Offline OP
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Originally Posted by Shannow
Originally Posted by OilUzer
I've read that thinner oil causes less heat but thicker oil will carry more heat (away) so I'm not sure about overall impact!


Where have you read that thicker carries away more heat ?

Interested in sources...

Per heat transfer, a heavier oil should carry more heat per unit volume, but that's about it.


I don't have a scientific source or any paper just the stuff I've read on bitog and wasn't sure what is true or not. Basically I would like to know (everything else aside), if an engine runs cooler with thinner oil or thicker oil or is it insignificant? I am talking about overall heat generation (friction and effects of oil viscosity) and heat transfer (from oil to oil cooler and engine block and effects of oil viscosity on that) .

Re: Sources of engine heat and effects of oil viscosity [Re: OilUzer] #4894416
10/12/18 03:06 AM
10/12/18 03:06 AM
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Shannow Offline
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Simplest example is my air cooled briggs...could be yours too.

Thermocouple down the filler/dipstick hole, and the thicker oil runs hotter...it has to, that's physics.
Thinner is cooler, until thinner to the point that something picks up, then temperature skyrockets on the way to failure (note to usual suspects, this is not saying that thin kills engines in every case, but thick can't kill until it can't pump on cold start).

Does that meet what you wanted ?


If you start on your own journey
And you find a path
...It's someone else's path.
Re: Sources of engine heat and effects of oil viscosity [Re: Shannow] #4894419
10/12/18 03:29 AM
10/12/18 03:29 AM
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OilUzer Offline OP
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Originally Posted by Shannow
Simplest example is my air cooled briggs...could be yours too.

Thermocouple down the filler/dipstick hole, and the thicker oil runs hotter...it has to, that's physics.
Thinner is cooler, until thinner to the point that something picks up, then temperature skyrockets on the way to failure (note to usual suspects, this is not saying that thin kills engines in every case, but thick can't kill until it can't pump on cold start).

Does that meet what you wanted ?



Yes kind of, my question regarding overall engine heat was if heavier oil carries more heat per unit volume (as you have mentioned above), isn't that same as what I said that I've read on bitog that thicker oil will carry more heat away? I am assuming heavier oil is thicker!

Re: Sources of engine heat and effects of oil viscosity [Re: OilUzer] #4894420
10/12/18 03:36 AM
10/12/18 03:36 AM
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Shannow Offline
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OK, thickness and density...yes the are typically correlated.

I am not stating that what you offered in your original post is correct, as you aren't even providing that which you claimed that you read, while claiming that I'm now supporting it.

Per the scary pictures in my first post...heat in the bearings transfers INTO the block, and is generated BY the viscous shearing...so how is thicker oil "carrying away more heat" ?

trip-trap-trip-trap...is that what I'm hearing ?


If you start on your own journey
And you find a path
...It's someone else's path.
Re: Sources of engine heat and effects of oil viscosity [Re: Shannow] #4894434
10/12/18 04:39 AM
10/12/18 04:39 AM
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OilUzer Offline OP
OilUzer  Offline OP
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Originally Posted by Shannow
OK, thickness and density...yes the are typically correlated.

I am not stating that what you offered in your original post is correct, as you aren't even providing that which you claimed that you read, while claiming that I'm now supporting it.

Per the scary pictures in my first post...heat in the bearings transfers INTO the block, and is generated BY the viscous shearing...so how is thicker oil "carrying away more heat" ?

trip-trap-trip-trap...is that what I'm hearing ?


I am not claiming that you are supporting everything i said ... It was just a question! It sounded to me that what I said (from my bitog reading) and what you said were the same thing as far as thicker oil being able to carry more heat. You called it more heat per unit volume .... I am no longer sure if we can agree on this or not! lol
However if we agree with the above (ability of heavier oil to carry more heat) then my main question was the overall impact. If the heavier oil which is causing extra heat is also taking some or most? of that extra heat (due to its ability to carry more heat vs. thinner oil) to the oil cooler or transfer more heat to engine block (contact surfaces) where the extra heat will dissipate in both cases ... So more heat is produced and more energy is lost (heat) but (again this is a question) not all that extra heat stays in the engine due to better efficiency of thicker oil (source of the problem/heat) in dissipating some (most?) of that extra heat. So your engine will run hotter but not as bad as you may think (relative to lighter oil) again based on my understanding of what I've read on bitog ... and I wanted to see how true that is hence my "overall impact" questiin.

Re: Sources of engine heat and effects of oil viscosity [Re: OilUzer] #4894454
10/12/18 05:38 AM
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OilUzer Offline OP
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Forgot to mention that one of my co-workers has a digital coolant,oil temp and trans oil temp readout. I asked him about engine temperatures after he switched from 0Wx20 to 5Wx30 ... and he said he hasn't noticed any differences and they are within the same range as before. His car has engine oil cooler and he has also added 2nd trans oil cooler and is into these kind of things and pays attention to gauges!

This is just one example and it is not a scientific test. I am sure his engine will run hotter with 5Wx30 but it hasn't been significant enough for him to notice. I guess it also depends on where the temperatures are taken...

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