Higher viscosity = higher operating temps?

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I saw a 10°F minimum temperature delta from 0W-20 to 0W-40 and wanted to see if my situation was unique or it was expected. There are always trade-offs and compromises between viscosities and one thing that stuck out for me was at what point is the increased temperature a detriment over the benefit of high viscosity oil.
 
IMO I doubt seriously if an end user would be able to discern the the difference. Just to many variables.

Now in controlled lab setting it would be possible measure the slight variation in temps.
 
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Originally Posted by 2015_PSD
I saw a 10°F minimum temperature delta from 0W-20 to 0W-40 and wanted to see if my situation was unique or it was expected. There are always trade-offs and compromises between viscosities and one thing that stuck out for me was at what point is the increased temperature a detriment over the benefit of high viscosity oil.

I personally wouldn't lose any sleep over it so long as engine temps are still in normal range. But if you were inclined to, you could hunt down the lowest noack Xw40 you could find to appease any concerns about evaporative loss...but then it's a ROI question, isn't it? Watch your dipstick levels on the Xw40..if you're not having to top off more than you normally do, then I'd say the diff' is a non starter. Just my 2 pennies...
 
Originally Posted by 2015_PSD
I saw a 10°F minimum temperature delta from 0W-20 to 0W-40 and wanted to see if my situation was unique or it was expected. There are always trade-offs and compromises between viscosities and one thing that stuck out for me was at what point is the increased temperature a detriment over the benefit of high viscosity oil.


Was this in your Rubicon? I'm thinking of going to a 5w-30 in my 2019 Wrangler (3.6L). Off road and while towing my camper I've seen oil temps hit 240. I'm a little skeptical about thin oil holding up.
 
Originally Posted by cb4017
Originally Posted by 2015_PSD
I saw a 10°F minimum temperature delta from 0W-20 to 0W-40 and wanted to see if my situation was unique or it was expected. There are always trade-offs and compromises between viscosities and one thing that stuck out for me was at what point is the increased temperature a detriment over the benefit of high viscosity oil.
Was this in your Rubicon? I'm thinking of going to a 5w-30 in my 2019 Wrangler (3.6L). Off road and while towing my camper I've seen oil temps hit 240. I'm a little skeptical about thin oil holding up.
Yes; and I have since swapped back and forth from 0W-20 to 0W-40 and back to 0W-20 and have seen similar temperatures from each viscosity--though the 0W-40 will go a little higher (2-4°F). This engine seems to run at higher temperatures than what I am used to seeing, but from what I see on the Jeep forums, it is pretty normal (cannot say that I like it though). The 3.6L Pentastar was originally specified to run 5W-30 and was used in other countries until 2019 when 0W-20 was specified and at this point all countries specify 0W-20. With that said, I would have no issues running 5W-30 in it and I will likely continue with 0W-40 as I have a large stash of it from my AMG.
 
Originally Posted by 2015_PSD
Originally Posted by cb4017
Originally Posted by 2015_PSD
I saw a 10°F minimum temperature delta from 0W-20 to 0W-40 and wanted to see if my situation was unique or it was expected. There are always trade-offs and compromises between viscosities and one thing that stuck out for me was at what point is the increased temperature a detriment over the benefit of high viscosity oil.
Was this in your Rubicon? I'm thinking of going to a 5w-30 in my 2019 Wrangler (3.6L). Off road and while towing my camper I've seen oil temps hit 240. I'm a little skeptical about thin oil holding up.
Yes; and I have since swapped back and forth from 0W-20 to 0W-40 and back to 0W-20 and have seen similar temperatures from each viscosity--though the 0W-40 will go a little higher (2-4°F). This engine seems to run at higher temperatures than what I am used to seeing, but from what I see on the Jeep forums, it is pretty normal (cannot say that I like it though). The 3.6L Pentastar was originally specified to run 5W-30 and was used in other countries until 2019 when 0W-20 was specified and at this point all countries specify 0W-20. With that said, I would have no issues running 5W-30 in it and I will likely continue with 0W-40 as I have a large stash of it from my AMG.

I'm run currently running 0W30 in my 2016 Rubicon, previously 5W30. I see no noticeable difference in temps from the spec 5W20.

I do agree they run hot, a lot hotter than I'm used to seeing.
 
Originally Posted by 2015_PSD
I saw a 10°F minimum temperature delta from 0W-20 to 0W-40 and wanted to see if my situation was unique or it was expected. There are always trade-offs and compromises between viscosities and one thing that stuck out for me was at what point is the increased temperature a detriment over the benefit of high viscosity oil.


Originally Posted by 2015_PSD
Yes; and I have since swapped back and forth from 0W-20 to 0W-40 and back to 0W-20 and have seen similar temperatures from each viscosity--though the 0W-40 will go a little higher (2-4°F). This engine seems to run at higher temperatures than what I am used to seeing, but from what I see on the Jeep forums, it is pretty normal (cannot say that I like it though). The 3.6L Pentastar was originally specified to run 5W-30 and was used in other countries until 2019 when 0W-20 was specified and at this point all countries specify 0W-20. With that said, I would have no issues running 5W-30 in it and I will likely continue with 0W-40 as I have a large stash of it from my AMG.

For a 0Wx0 full synthetic oil , I won't be bothered with operating temperature range of 80*C (180*F) and 105*C (220*F) in the context of temperature-driven 'accelerated' oil oxidation.
Instead a thicker oil in 0W40 'gains' higher MOFT over a thinner oil in 0W20 or 0W30 at no additional purchase cost , in fact lower cost in my market .
 
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I have agreed for a long time on the bearing thing but here is why, just found this,

"Too thick oil, wonderful oil pressure, yet parts inside the engine could actually be starved for oil due to lowered volume. Another downer, circulating oil accounts for nearly 50% of engine cooling, so reduced oil-flow reduces cooling causing lubricated parts to operate at higher temperatures. Higher parts temperatures, more wear."

Source, Click here

I do know for a fact (menaing have seen photos) that in many motorycycle transmissions where the person ran a heavy weight gear oil, the transmission bearings were very dark color to black which would indicate heat. Mind you, this is not the reason the transmission was being serviced, just an observation by a technician who took photos on many blackened bearings over time.
 
Originally Posted by gfh77665
Your 5w-30 ends up being a 5w-20 before you change it anyway...

According to the UOAs I had done mine hasn't.
 
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Originally Posted by demarpaint
Originally Posted by gfh77665
Your 5w-30 ends up being a 5w-20 before you change it anyway...

Mine hasn't.

It's a ridiculous argument anyway. If a 30 shears down, then a 20 will too.
 
*Does the Rubicon OM list additional approved oil viscosities - or just the one ? In my Hyundai/Kia the OM lists 5W20 , 5W30 or 10W30 as being allowed - with the caveat that oil viscosity should be chosen based on the anticipated ambient temps during the upcoming OCI . I take this Hyundai/Kia statement to read : "While 5W20 is acceptable - 5W30 or 10W30 will provide more engine protection during the summer months" .
 
Originally Posted by CR94
Originally Posted by ChrisD46
The answer for most people is to equally mix mix 5W20 / 5W30 oil of the same type and manufacturer - theoretically the best of both worlds for oil film thickness and flow to tighter tolerance engine parts and keep OCI's of less than 5K miles.
So the 5W-30 part maintains a thick film, while the 5W-20 part reaches out into "tighter tolerance engine parts" where only it can fit?

What parts in an engine have a clearance so tight [ tolerance is the allowed variance of the clearance ] that only a 20 wt will reach?
 
Originally Posted by DGXR
Thicker oil usually generates higher oil pressure, and since physics tells me that higher pressures equal higher temperatures, yes I can see a thicker oil leading to higher oil temps. Not to mention the engine is working harder to pump the thicker oil, generating more heat. And other things mentioned above. Makes sense to me.

It takes more power to move the oil .
 
Originally Posted by rooflessVW
Originally Posted by demarpaint
Originally Posted by gfh77665
Your 5w-30 ends up being a 5w-20 before you change it anyway...

Mine hasn't.

It's a ridiculous argument anyway. If a 30 shears down, then a 20 will too.


The 30 grade shearing down to a 20 is getting old fast. In a healthy engine with a good oil, running sane intervals there should be no problems with a 30 grade dropping to a 20 grade.
 
Originally Posted by ChrisD46
*Does the Rubicon OM list additional approved oil viscosities - or just the one ? In my Hyundai/Kia the OM lists 5W20 , 5W30 or 10W30 as being allowed - with the caveat that oil viscosity should be chosen based on the anticipated ambient temps during the upcoming OCI . I take this Hyundai/Kia statement to read : "While 5W20 is acceptable - 5W30 or 10W30 will provide more engine protection during the summer months" .
No; globally from 2019 onwards, they only specify 0W-20 for the 3.6L and 0/5W-30 for the 2.0L Turbo
 
Originally Posted by alarmguy
I have agreed for a long time on the bearing thing but here is why, just found this, "Too thick oil, wonderful oil pressure, yet parts inside the engine could actually be starved for oil due to lowered volume. Another downer, circulating oil accounts for nearly 50% of engine cooling, so reduced oil-flow reduces cooling causing lubricated parts to operate at higher temperatures. Higher parts temperatures, more wear."
I am not concerned with "oil starvation"; modern engines have positive displacement pumps and the oil pressure remained the same for both oils (about 31 PSI at highway speeds). At 210-225°F oil temperatures, I would have to believe the oil is "thin enough" to reach all of the critical places.
 
Originally Posted by zeng
Originally Posted by 2015_PSD
I saw a 10°F minimum temperature delta from 0W-20 to 0W-40 and wanted to see if my situation was unique or it was expected. There are always trade-offs and compromises between viscosities and one thing that stuck out for me was at what point is the increased temperature a detriment over the benefit of high viscosity oil.


Originally Posted by 2015_PSD
Yes; and I have since swapped back and forth from 0W-20 to 0W-40 and back to 0W-20 and have seen similar temperatures from each viscosity--though the 0W-40 will go a little higher (2-4°F). This engine seems to run at higher temperatures than what I am used to seeing, but from what I see on the Jeep forums, it is pretty normal (cannot say that I like it though). The 3.6L Pentastar was originally specified to run 5W-30 and was used in other countries until 2019 when 0W-20 was specified and at this point all countries specify 0W-20. With that said, I would have no issues running 5W-30 in it and I will likely continue with 0W-40 as I have a large stash of it from my AMG.

For a 0Wx0 full synthetic oil , I won't be bothered with operating temperature range of 80*C (180*F) and 105*C (220*F) in the context of temperature-driven 'accelerated' oil oxidation.
Instead a thicker oil in 0W40 'gains' higher MOFT over a thinner oil in 0W20 or 0W30 at no additional purchase cost , in fact lower cost in my market .
Zeng - agreed and since both oils are within a few degrees of each other, the MOFT provided by the 0W-40 has some benefits over the 0W-20 when working the engine.
 
Run nothing but 20 weight in mine and no issues. Spent many consecutive days in Moab heat, 20 hour drive each way, etc etc. The Pentastar just doesn't seem very hard on oil at all, usually do about 7-7.5k OCI. Absolutely tons of oil pressure too. I've never tried a 30 weight because it doesn't at all seem necessary based on my results with 20 weight.
 
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