Higher viscosity = higher operating temps?

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Has anyone seen an oil temperature increase by moving from say an xW-20 to an xW-40 (with everything remaining the same)?
 
Yep,
5W20 to 25W60 in my Briggs and Straton makes quite a difference.

That was an air cooled engine, so you won't see a coolant temperature change.

My old J-Car, lost a few MPG going SAE30 to 25W70...that's ALL oil related heat.
 
I went from 5w-20 to 0w-40 (with 5w-30 in between) in my 2013 F150 (5.0), with no discernible difference in mpg or power.

I imagine going to a 70 (! dang Shannow) might have made a difference....there's thick, then there's TOO thick.
 
Originally Posted by 2015_PSD
Has anyone seen an oil temperature increase by moving from say an xW-20 to an xW-40 (with everything remaining the same)?

I'd say the new Xw-40 lube isn't moving as freely (reduced flow) throughout the engine, as compared to the previous Xw20 lube? You would get more heat if the oil film weren't as thick as the previous lube but I would expect that to happen (potentially) if you went down in viscosity, not up.

I suppose it's possible to see a noticeable rise in oil temp related to oil drag..too thick of an oil can actually increase wear (rate) on some components.
 
Yes. Street stock engines running 5000-7000 rpm sustained at near WOT the entire time. On 20w-50, the oil temp hangs around 280*F. On 10w-30, it never tops 260*F.

In my own car, sticking with 5w-30 all year around produced the same 220-230*F oil temps all year around. Going to 5w-40 in the summer increased temps to near 240*F.
 
Interesting question. Since the answer appears to be yes, then why is this the case? Is it that the engine has to work harder, to push through a thicker oil? Or is it that a thicker oil will absorb heat better? If I understand Mad Hatter correctly, he is saying that it is the first--that the engine has to work harder?

Originally Posted by Mad_Hatter
I suppose it's possible to see a noticeable rise in oil temp related to oil drag..too thick of an oil can actually increase wear (rate) on some components.
 
Originally Posted by JLTD
I went from 5w-20 to 0w-40 (with 5w-30 in between) in my 2013 F150 (5.0), with no discernible difference in mpg or power.

I imagine going to a 70 (! dang Shannow) might have made a difference....there's thick, then there's TOO thick.


Currently have 15W-60 in my Volvo, and no noticeable in crease in temp or fuel consumption...that's just using a temp gun on the sump, and it has a heat exchanger in the top tank, so basically running at coolant temp. In fact my best ever fuel consumption has been done on the 15W-60 - 7 litres per 100km for 100km open road...33.6 mpgUS., 40mpg UK.
 
Originally Posted by Silk
Originally Posted by JLTD
I went from 5w-20 to 0w-40 (with 5w-30 in between) in my 2013 F150 (5.0), with no discernible difference in mpg or power.

I imagine going to a 70 (! dang Shannow) might have made a difference....there's thick, then there's TOO thick.


Currently have 15W-60 in my Volvo, and no noticeable in crease in temp or fuel consumption...that's just using a temp gun on the sump, and it has a heat exchanger in the top tank, so basically running at coolant temp. In fact my best ever fuel consumption has been done on the 15W-60 - 7 litres per 100km for 100km open road...33.6 mpgUS., 40mpg UK.


Wish i could get Penrite in Spain, specially some HPR30 20W-60...
Just the thought of that lovely bright stock base with 1600ppm of ZDDP makes my mouth water
20.gif
 
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Originally Posted by zeng
It's rpm driven under light load condition , IMHO.


No one achieves best fuel economy at max revs and wide open throttle...max manifold vacuum is best. But I never got better economy with lighter oils in the same conditions. And as they say - ''Your results may differ.''
 
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Originally Posted by paulri
Interesting question. Since the answer appears to be yes, then why is this the case? Is it that the engine has to work harder, to push through a thicker oil? Or is it that a thicker oil will absorb heat better? If I understand Mad Hatter correctly, he is saying that it is the first--that the engine has to work harder?

Tolerances determine the ideal viscosity..too thick of an oil and starvation and drag (resistance) can be a problem; too thin of an oil and oil film thickness can become an issue in preventing metal to metal contact.

The thicker the oil, the harder the engine has to work to push that oil through the engine, filter etc. This (engine working harder) will cause an increase, on some level, of engine temps. This is also why high viscosity oils are not designated resource conserving (increased fuel consumption). In addition, higher viscosity oils have larger molecules and when an oil ages and the lighter molecules burn off you have a high(er) concentration of those larger molecules (think sludge) that can cause wear in areas of tight tolerance (think bearings). Now synthetics are designed to have uniform molecules that better withstand thermal breakdown as compared to mineral oil. The higher the quality of the synthetic base oil, the more uniform the molecules are and better thermal stability. I believe that the same holds for the type and quality of the viscosity modifiers used.

I'm just a regular Joe trying to relate stuff I've read, so if I've got something wrong please chime in.

There's a lot out there on oil drag but here's some stuff that you might find useful..

Viscosity

Viscosity 2
 
Oh, so that's all good then, my 15W-60 is ester POA and the uniform molecules are what give me the better fuel economy.
 
Originally Posted by Silk
Oh, so that's all good then, my 15W-60 is ester POA and the uniform molecules are what give me the better fuel economy.

Or even if you're running a grp2 oil, just don't push it past it's break point...oil that's breaking down is going to increase the operating temp and rob your engine of hp, fuel efficiency and increase wear rate.
 
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Originally Posted by paulri
Interesting question. Since the answer appears to be yes, then why is this the case? Is it that the engine has to work harder, to push through a thicker oil? Or is it that a thicker oil will absorb heat better? If I understand Mad Hatter correctly, he is saying that it is the first--that the engine has to work harder?

Originally Posted by Mad_Hatter
I suppose it's possible to see a noticeable rise in oil temp related to oil drag..too thick of an oil can actually increase wear (rate) on some components.



People get enamoured with the pumping and "flow"...that' not it. Pumping is less than turning on your headlights.

The real losses are in viscous drag in the bearings (and bearing surfaces like piston rings)...in fact, some OTR engine designs of the future will include thermal barrier coatings in the mid stroke area to artificially reduce the viscosity in the mid stroke region.
 
I keep the oil temp up on my MFD and I definitely noticed an increase in temps the first time I used a higher HTHS 5W30 (M1 ESP Formula, HTHS was 3.58 compared to the vanilla M1 5W30 I had been using at 3.1). I don't remember the exact temp ranges anymore, but I think I posted at the time that they went up 5-10F with the ESP.
Since I was used to seeing fairly consistent temp ranges with some dependence upon the seasons (typically a bit cooler in the winter) over some tens of thousands of miles and I made this change in the summer, I was pretty alarmed to see the temp range move up all of a sudden. I actually posted a panicky thread about it on subaruforester.org and some knowledgeable folks there let me know that was exactly what was to be expected...more viscous oil, higher oil temps.
 
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.
 
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?
 
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.
 
Originally Posted by Shannow
...in fact, some OTR engine designs of the future will include thermal barrier coatings in the mid stroke area to artificially reduce the viscosity in the mid stroke region.

Is that possible with the speed the piston moves through that area?
 
Originally Posted by ka9mnx
Originally Posted by Shannow
...in fact, some OTR engine designs of the future will include thermal barrier coatings in the mid stroke area to artificially reduce the viscosity in the mid stroke region.

Is that possible with the speed the piston moves through that area?


Certainly is...it's the speed of the piston moving through the area that makes it attractive
https://core.ac.uk/download/pdf/9591723.pdf
 
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