Thicker oil runs hotter so I end with the same protection due to lower viscosity?

B

Bmsluite

Joined
Feb 9, 2021
Messages
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Context: I have a track car and these temperatures are from circuit racing.

Car is 2007 350z with slightly built VQ35HR. Cams, lights eight rods and pistons, tune.
8300 rpm redline

I used to run 0w-40 M1
Temps were around 245-255F after half an hour in track where it leveled out.

Switched to Castrol 5w-40 euro.
Temps are now 275-285F after half an hour

So a thicker oil viscosity. But there is so much more heat from the higher viscosity that I almost think it actually ends up thinner.

Am I actually better off running a 5w-30? Would it run even cooler?

I feel like a thinner oil at a lower temperature would be better than a thicker oil at a higher temperature.

What is your opinion?
More importantly, what are facts you have to back it up?
 
I'm thinking the difference in oil temperature had little to due with the oil grade, and a lot more to do with differences in ambient temperature or how hard you were pushing on track.

I've seen a study that compared oil temps with oil grades ranging from SAE 20 to SAE 60, and I think the difference was only 6-7°C. The difference between 0W-40 and 5W-40 should hardly be measurable.
 
If you had any controls on your experiment then perhaps you'd have something.

Here are a few previous discussions, perhaps one or more of these may help. There are more:

teambeechstreet

Thread 'Thicker oil make engine run hotter?'

This is a noob question, but does thicker oil actually make the engine run hotter? I have an 87 civic with the 1.5 w/220K miles (which calls for 10w30)and have ran 10w30, 10w-40, and 15w40, and the temp gauge needle always sat at about the half mark. The day I changed the oil out to 2 qrts of Trop Artic 10w30 synth blend, half a qrt of Mobil 1 10w30 that I had laying around, and 1 qrt of SuperTech 20w-50 to help with some oil burning issues, I noticed the temp gauge needle sat at the 3/4s mark and thats where its been for the past 800 miles. Could it be because of the qrt of 20w-50...
G

Thread 'Is higher heat a benefit of thicker oil?'

Since lower viscosity oil circulates better than higher viscosity oil in an internal combustion engine, it should lower the temperature of the engine. But, would thicker oil that gives a higher engine temperature be better for short distance driving since it will minimize condensation as the heat is higher to burn off moisture in the engine? Just curious.
O

Thread 'Sources of engine heat and effects of oil viscosity'

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.gif
it is not my intention to turn this into thick vs. thin...
V

Thread 'Overheating engine... run Thin or Thick oil?'

My ancient 1 liter/3 cylinder car likes to overheat when climbing steep mountain grades during California summers. 5W20 is the recommended oil, but I switched to 5W40 for more high temperature protection.

Thinner or Thicker?
Which is better for a very hot engine?
 
To the op, after you did your engine work, did you change anything in the cooling system?. like a lower temp thermostat ?, or a higher capacity radiator?, or maybe having your cooling fan come on sooner?. Or are you just expecting a different grade of oil to provide perfect cooling?. Just wondering.,,
 
BigCahuna said:
To the op, after you did your engine work, did you change anything in the cooling system?. like a lower temp thermostat ?, or a higher capacity radiator?, or maybe having your cooling fan come on sooner?. Or are you just expecting a different grade of oil to provide perfect cooling?. Just wondering.,,
Click to expand...
Or, as pointed out above, does the OP have any controls on the experiment?
 
Bmsluite said:
Context: I have a track car and these temperatures are from circuit racing.

Car is 2007 350z with slightly built VQ35HR. Cams, lights eight rods and pistons, tune.
8300 rpm redline

I used to run 0w-40 M1
Temps were around 245-255F after half an hour in track where it leveled out.

Switched to Castrol 5w-40 euro.
Temps are now 275-285F after half an hour

So a thicker oil viscosity. But there is so much more heat from the higher viscosity that I almost think it actually ends up thinner.

Am I actually better off running a 5w-30? Would it run even cooler?

I feel like a thinner oil at a lower temperature would be better than a thicker oil at a higher temperature.

What is your opinion?
More importantly, what are facts you have to back it up?
Click to expand...
Mobil1 0W40 FS is intro track oil for XOM. castrol Edge 5W40 is step or two down. If you want to run Castrol, run 0W40.
I ran M1 0W40 to 300f on track. Still did 5k OCI (before I installed radiator type oil cooler).
245/255f is piece of cake on track. Another good oils are Pennzoil Platinum Euro 5W40, Motul X-Cess 5W40 GEN2.

Now, that is BIG difference. That is not due to thickness but outside factors. That difference is equal to installing radiator type oil cooler all things being equal.
Castrol 5W40 is not thicker than current M1 0W40. Castrol 5W40 HTHS is 3.64cP while M1 0W40 is 3.7-3.8cP. So if anything, M1 has more resistance.
 
Controls are the temps are 20-30 hotter with this oil in cooler temperatures.

I never broke 265 with this same setup in 100F weather.

This year never broke 90F and I'm running hotter.

Seriously? Just assume I cna not find a pattern.
This was a true waste of time to post
 
Bmsluite said:
Controls are the temps are 20-30 hotter with this oil in cooler temperatures.

I never broke 265 with this same setup in 100F weather.

This year never broke 90F and I'm running hotter.

Seriously? Just assume I cna not find a pattern.
This was a true waste of time to post
Click to expand...
Why was it a waste?
Have you considered other issues? Cooling system?
Again, M1 is actually a thicker oil due to higher HTHS. HTHS is what matters, not KV100. The composition of oil could have a small influence, but nothing like that.
 
Bmsluite said:
Controls are the temps are 20-30 hotter with this oil in cooler temperatures.

I never broke 265 with this same setup in 100F weather.

This year never broke 90F and I'm running hotter.

Seriously? Just assume I cna not find a pattern.
This was a true waste of time to post
Click to expand...
I don't think it was a waste of time. However, the variable values you provided are not sufficient to conclude. When you say, "there is so much more heat", one can assume there's more than just a change of oil (with the same approvals).
 
I run about 15 track a days a year. Every year. Year after year. Same setup.

I know when the oil is running hotter.

I even added some director plates around the cooler. That dropped the temps by a good 15 degrees.

The only change this year was the oil and new tires. Pretty sure the tires aren't heating up the oil.

People assume everyone is dumb, which is rude.
 
Do certain oils just run cooler? Even similar viscosity? If so, what are the factors that would cause one oil to run cooler than another?
 
For reference, there is a large, 20"x 12" bar and plate dual pass oil cooler in front of the radiator with director plates fed from the bumper inlet.

200F thermostat on a sandwich plate. Very short run of hose from cooler to plate
 
Bmsluite said:
I run about 15 track a days a year. Every year. Year after year. Same setup.

I know when the oil is running hotter.

I even added some director plates around the cooler. That dropped the temps by a good 15 degrees.

The only change this year was the oil and new tires. Pretty sure the tires aren't heating up the oil.

People assume everyone is dumb, which is rude.
Click to expand...
What is the weight difference between old tires and new tires? Unsprung weight is a significant contributor to loss of performance, hence it is harder to accelerate or decelerate. You will need more energy.
I would bet on tires if that is the only contributor. You may have a cooling issue that is not yet manifesting as a problem. Yet.
Now, you can always move back to M1 and check.
 
The biggest contributor to oil heat is hydrodynamic friction, followed by combustion heat. A higher viscosity, more specifically a higher dynamic viscosity, will generate more hydrodynamic friction which contributes more heat. However, the difference between a 0W-40 and 5W-40 will be minimal, if anything at all, as they are similar viscosity at operating temperature. A bigger difference would be seen from the formula itself with factors like differing specific heat capacity and transfer coefficient between different base oils.
 
Tires are two pounds heavier though I had already run two track days with the old tires hut with the different oil. Temps were greatly increased then too.

It did go up slightly with the newer tires. But that is most likely because they are. So they have more grip. So I can get into throttle earlier. This happens everytime I swap tires. Fresh tires always increase the temps a little. But not this much
 
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