Does cooler oil = better oil?

[Shiberu]

Hi guys,

I am curious, on whether a cooler running oil under load is generally considered better than a hotter oil running under load.

Some context, I am currently running the Motul 300V and am seeing about 90 degrees Celsius on idle and about 115 degrees Celsius during high loads (track days etc.). I have been approached by guys who were promoting their brand of oil and they touted the temperature of the oil on idle and load are 5-10 degrees Celsius lower than my readings. This being the same engine and configuration of the car. If this stands true, would this brand of oil be in any way superior?

As I understand the heat generated by the engine has to go somewhere and normally would be absorbed by the engine oil or dissipated by the coolant. So wouldn't a cooler running engine oil be considered "bad" as it does not take in the heat from the engine block? Do advise if I got this concept wrongly.

Thanks!

 

[SirTanon]

I have to wonder if they were actually trying to sell you on the other side of that spectrum - Inferring that the oil was so good that it reduced the internal friction so much that it resulted in less heat inside the engine.

I call [censored], either way.

 

[Shannow]

A lot of the temperature in the oil, i.e. the heat that it is carrying away is generated within bearing surfaces themselves, by the shearing action across the oil film (i.e. bearings, piston skirts), while a smaller component is heat that is carried away from hot components like pistons (via squirters and splash).

In order to run cooler, the oil has to produce lower internal friction, aka viscosity.

In reducing viscosity, you CAN reduce temperature rise, but also reduce the Minimum Oil Film Thickness that keeps parts away from each other.

 

[Shiberu]

Originally Posted By: Shannow
A lot of the temperature in the oil, i.e. the heat that it is carrying away is generated within bearing surfaces themselves, by the shearing action across the oil film (i.e. bearings, piston skirts), while a smaller component is heat that is carried away from hot components like pistons (via squirters and splash).

In order to run cooler, the oil has to produce lower internal friction, aka viscosity.

In reducing viscosity, you CAN reduce temperature rise, but also reduce the Minimum Oil Film Thickness that keeps parts away from each other.


Surprisingly, or not, the viscosity grade given were in similar specifications to mine, 5W-40. So I would think maybe... some sort of additive package?

 

[Shannow]

e.g. divide in each case the "Watts" by the "flow rate' to get a feel for which increases temperature more...then look at the effect on MOFT (parts separation)

 

[Johnny2Bad]

There is an ideal temperature (or more precisely, temperature range) where your oil should fall. Too cold is not good, and neither is too hot.

In many cases the oil cooler is sized in such a way that it operates within the desired parameters most, if not all, of the time. However in some cases, and especially if you are dealing with an aftermarket cooler where it may or may not be sized correctly, a thermostatic valve is recommended, so that the oil is not run through the cooler unless it is at a certain minimum temperature.

Emissions-wise the oil temperature your motor was designed for is about 185F minimum, and, although this is very dependent on exactly where the temperature is measured, perhaps 260F maximum. The higher value is just a ballpark example; there are many variables you would take into account before coming up with a value specific to your engine and operating conditions.

In racing or off-road applications, maximum power is generated when the oil is a bit cooler, I would expect it to vary and be engine-dependent, but for example in the Miata 1.8 it likes about 175F in the sump as an ideal (best power) temperature, but this is for modified engines (with aftermarket engine control computer) only.

In any case, motor oil tends to retain heat and dissipate that heat very slowly. So it is much easier to heat motor oil than cool it.

 

[Ducked]

For a given oil, cooler is thicker.

And thicker oil.....is better (for wear protection) and worse (for fuel economy).

But a different oil that runs cooler probably does so because its thinner

And thinner oil..... is worse (for wear protection) and better (for fuel economy)

So you takes your pick, and you pays your money.

Or you dont.

I wouldn't

 

[Ducked]

Are the higher minimum thicknesses at the higher RPM due to higher oil pressures or some hydrodynamic self-centering effect.

I'm guessing latter.

 

[Shannow]

Originally Posted By: Ducked
Are the higher minimum thicknesses at the higher RPM due to higher oil pressures or some hydrodynamic self-centering effect.

I'm guessing latter.


Yep, more curves when I get home...

 

[zeng]

Originally Posted By: Shiberu
Originally Posted By: Shannow
A lot of the temperature in the oil, i.e. the heat that it is carrying away is generated within bearing surfaces themselves, by the shearing action across the oil film (i.e. bearings, piston skirts), while a smaller component is heat that is carried away from hot components like pistons (via squirters and splash).

In order to run cooler, the oil has to produce lower internal friction, aka viscosity.

In reducing viscosity, you CAN reduce temperature rise, but also reduce the Minimum Oil Film Thickness that keeps parts away from each other.


Surprisingly, or not, the viscosity grade given were in similar specifications to mine, 5W-40. So I would think maybe... some sort of additive package?

Assuming this oil A has similar KV@40/KV@100 as Motul 300V, then it's superior to Motul in terms of :
a)having effective friction-reducing solid lubricants like moly etc in its add pack lowering oil temperatures as claimed;
b)delivering better FE through friction reduction, and
c)providing stronger wear protection through higher operating viscosity.
JMHO.

 

[zeng]

Originally Posted By: Shannow

e.g. divide in each case the "Watts" by the "flow rate' to get a feel for which increases temperature more...then look at the effect on MOFT (parts separation)


Nice tables.
Appreciate if we could have its operating temperatures/viscosities in Tables 7&8 ..

 

[UltrafanUK]

A cooler oil might make a very slight reduction in wear during track use or heavy hot towing applications, BUT it will make no difference in normal use.

 

[Shannow]

Originally Posted By: zeng
Nice tables.
Appreciate if we could have its operating temperatures/viscosities in Tables 7&8 ..

http://www.eng.auburn.edu/~jacksr7/SAE2002013355.pdf

Here's another one that shatters a few BITOG myths as well...

http://www.substech.com/dokuwiki/doku.ph...engine_bearings

 

[Shiberu]

Originally Posted By: zeng
Originally Posted By: Shiberu
Originally Posted By: Shannow
A lot of the temperature in the oil, i.e. the heat that it is carrying away is generated within bearing surfaces themselves, by the shearing action across the oil film (i.e. bearings, piston skirts), while a smaller component is heat that is carried away from hot components like pistons (via squirters and splash).

In order to run cooler, the oil has to produce lower internal friction, aka viscosity.

In reducing viscosity, you CAN reduce temperature rise, but also reduce the Minimum Oil Film Thickness that keeps parts away from each other.


Surprisingly, or not, the viscosity grade given were in similar specifications to mine, 5W-40. So I would think maybe... some sort of additive package?

Assuming this oil A has similar KV@40/KV@100 as Motul 300V, then it's superior to Motul in terms of :
a)having effective friction-reducing solid lubricants like moly etc in its add pack lowering oil temperatures as claimed;
b)delivering better FE through friction reduction, and
c)providing stronger wear protection through higher operating viscosity.
JMHO.


Those are very good points. In which that had me digging for some data for Oil A's KV values. I have very limited knowledge on viscosity so I cannot really deduce much by comparing the data. Perhaps this would be a good time for me to grasp the concept of Kinematic Viscosity.

From Oil A's website
KV@40°C - 77 mm2/s
KV@100°C - 12.49 mm2/s

Grabbing from Motul's data sheet for 300V 5W-40
KV@40°C - 74.2 mm2/s
KV@100°C - 13.1 mm2/s

Would the KV @ 100°C for Oil A be "superior" in a sense where it is less viscous as compared to the Motul's just by comparing said data?

 

[Shiberu]

Originally Posted By: Shannow

e.g. divide in each case the "Watts" by the "flow rate' to get a feel for which increases temperature more...then look at the effect on MOFT (parts separation)



Thanks for this resource.

Originally Posted By: Shannow
Originally Posted By: zeng
Nice tables.
Appreciate if we could have its operating temperatures/viscosities in Tables 7&8 ..

http://www.eng.auburn.edu/~jacksr7/SAE2002013355.pdf

Here's another one that shatters a few BITOG myths as well...

http://www.substech.com/dokuwiki/doku.ph...engine_bearings


This is awesome reading material. Starting to love this forum more and more.

 

[Food Scientist]

Could it be the salesman didn't know you were running a high dollar oil to begin with and thinks that his oil will have a lot more friction modifier than yours and therefore reduce the amount of friction while maintaining viscosity, lowering the temperature of the oil?

 

[Ducked]

Originally Posted By: Shiberu
Originally Posted By: zeng
Originally Posted By: Shiberu
Originally Posted By: Shannow
A lot of the temperature in the oil, i.e. the heat that it is carrying away is generated within bearing surfaces themselves, by the shearing action across the oil film (i.e. bearings, piston skirts), while a smaller component is heat that is carried away from hot components like pistons (via squirters and splash).

In order to run cooler, the oil has to produce lower internal friction, aka viscosity.

In reducing viscosity, you CAN reduce temperature rise, but also reduce the Minimum Oil Film Thickness that keeps parts away from each other.


Surprisingly, or not, the viscosity grade given were in similar specifications to mine, 5W-40. So I would think maybe... some sort of additive package?

Assuming this oil A has similar KV@40/KV@100 as Motul 300V, then it's superior to Motul in terms of :
a)having effective friction-reducing solid lubricants like moly etc in its add pack lowering oil temperatures as claimed;
b)delivering better FE through friction reduction, and
c)providing stronger wear protection through higher operating viscosity.
JMHO.


Those are very good points. In which that had me digging for some data for Oil A's KV values. I have very limited knowledge on viscosity so I cannot really deduce much by comparing the data. Perhaps this would be a good time for me to grasp the concept of Kinematic Viscosity.

From Oil A's website
KV@40°C - 77 mm2/s
KV@100°C - 12.49 mm2/s

Grabbing from Motul's data sheet for 300V 5W-40
KV@40°C - 74.2 mm2/s
KV@100°C - 13.1 mm2/s

Would the KV @ 100°C for Oil A be "superior" in a sense where it is less viscous as compared to the Motul's just by comparing said data?



If I understand the above points correctly, it's being suggested that the difference is due to friction modifying additives. If there is such a difference, I don't think it would necessarily be reflected in the viscosities.

Molybdenum FM surface-binds, and is specifically effective in boundary lubrication, so it wouldn't be expected to affect viscosity.

It would only affect temperature where there is surface contact, which in normal operation is mostly restricted to cams and piston rings.