My previous two fills in the CTS-V have been with 5w30 G-Oil. I switched to 5w40 Rotella T6 and I didn't notice it right away but my hot oil temps went from a norm of about 201-203 degrees to 215-217. Is this a result of the weight difference, the additive package, or both possibly?
Switched oil now oil temp is higher.
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It would be a result of viscosity difference, but I don't think the different grade would affect temperature that much.
In theory though, a thinner oil flows better, transferring heat more effectively. This is consistent with the situation you described, but your temp change seems more drastic.
In theory though, a thinner oil flows better, transferring heat more effectively. This is consistent with the situation you described, but your temp change seems more drastic.
Originally Posted By: mount
In theory though, a thinner oil flows better, transferring heat more effectively. This is consistent with the situation you described, but your temp change seems more drastic.
That's BITOG myth. Positive displacement pumps are simply that, and there's not enough variance to do that purely through heat transfer, and thinner oils have a higher internal pump leakage...
A thicker oil has a greater temperature rise across the bearing, as the engine has to do more "work" on the oil...but there are those here (thinner oil proponents) who do not "feel" that this is true.
My view ?
The thicker oil requires more work in the bearings. work = heat.
Heat needs to be "pushed" into the atmosphere. more heat means more temperature. Heat transfer is referenced back to 0 degrees K for calculation purposes, so 10F is really only a percent and a half temperature rise.
In theory though, a thinner oil flows better, transferring heat more effectively. This is consistent with the situation you described, but your temp change seems more drastic.
That's BITOG myth. Positive displacement pumps are simply that, and there's not enough variance to do that purely through heat transfer, and thinner oils have a higher internal pump leakage...
A thicker oil has a greater temperature rise across the bearing, as the engine has to do more "work" on the oil...but there are those here (thinner oil proponents) who do not "feel" that this is true.
My view ?
The thicker oil requires more work in the bearings. work = heat.
Heat needs to be "pushed" into the atmosphere. more heat means more temperature. Heat transfer is referenced back to 0 degrees K for calculation purposes, so 10F is really only a percent and a half temperature rise.
Is the higher heat in the thicker oil , heat removed from bearing and cyl wall surfaces?
Originally Posted By: spasm3
Is the higher heat in the thicker oil , heat removed from bearing and cyl wall surfaces?
No. It's because thicker oil is a little harder to pump through the engine and builds up slightly higher oil temps. This link may help explain this a little better.
http://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_1_Advanced_Fuel_Economy.aspx
Is the higher heat in the thicker oil , heat removed from bearing and cyl wall surfaces?
No. It's because thicker oil is a little harder to pump through the engine and builds up slightly higher oil temps. This link may help explain this a little better.
http://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_1_Advanced_Fuel_Economy.aspx
Last edited:
Originally Posted By: Shannow
That's BITOG myth. Positive displacement pumps are simply that, and there's not enough variance to do that purely through heat transfer, and thinner oils have a higher internal pump leakage...
Common sense, maybe a BITOG myth, would suggest it is the higher oil pressure when using a higher viscosity lube that causes higher internal pump leakage. Is this not the case?
That's BITOG myth. Positive displacement pumps are simply that, and there's not enough variance to do that purely through heat transfer, and thinner oils have a higher internal pump leakage...
Common sense, maybe a BITOG myth, would suggest it is the higher oil pressure when using a higher viscosity lube that causes higher internal pump leakage. Is this not the case?
Originally Posted By: Shark
My previous two fills in the CTS-V have been with 5w30 G-Oil. I switched to 5w40 Rotella T6 and I didn't notice it right away but my hot oil temps went from a norm of about 201-203 degrees to 215-217. Is this a result of the weight difference, the additive package, or both possibly?
The viscosity difference could have a slight impact on the temp, but I'm going to go out on a limb and say that the temperature difference is mostly due to the difference in thermal properties of the two base oils. G-Oil is ester-based, while T6 is hydrocarbon-based. The two base oils probably have slightly different heat capacities - meaning one will heat up and cool down a little 'faster' than the other. This could result in a slightly different temperature at your oil temp gauge.
My previous two fills in the CTS-V have been with 5w30 G-Oil. I switched to 5w40 Rotella T6 and I didn't notice it right away but my hot oil temps went from a norm of about 201-203 degrees to 215-217. Is this a result of the weight difference, the additive package, or both possibly?
The viscosity difference could have a slight impact on the temp, but I'm going to go out on a limb and say that the temperature difference is mostly due to the difference in thermal properties of the two base oils. G-Oil is ester-based, while T6 is hydrocarbon-based. The two base oils probably have slightly different heat capacities - meaning one will heat up and cool down a little 'faster' than the other. This could result in a slightly different temperature at your oil temp gauge.
Thick oil cannot dissipate heat as fast. My Harley's runs 15f cooler using a 15w-40 instead of 20w-50.
Switch back to the right oil and oil temps will go back to normal.
Switch back to the right oil and oil temps will go back to normal.
MolaKule
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Quote:
I didn't notice it right away but my hot oil temps went from a norm of about 201-203 degrees to 215-217
I can believe it.
The pressure lubrication system in an engine is basically a hydraulic system which pumps fluid around the engine for mainly cooling purposes.
A fluid pump requires more energy input to move thicker fluids. That increased energy is also deposited in the oil.
That increased amount of energy deposited in the oil raises the oil's temperature. In Physics we say that E is approximately equal to kT. That is, the more energy you have to put into a system, the temperature of that system will rise.
I didn't notice it right away but my hot oil temps went from a norm of about 201-203 degrees to 215-217
I can believe it.
The pressure lubrication system in an engine is basically a hydraulic system which pumps fluid around the engine for mainly cooling purposes.
A fluid pump requires more energy input to move thicker fluids. That increased energy is also deposited in the oil.
That increased amount of energy deposited in the oil raises the oil's temperature. In Physics we say that E is approximately equal to kT. That is, the more energy you have to put into a system, the temperature of that system will rise.
It's not the oil pump...on 8GPM, 20psi increase in oil pressure (certainly more than would be seen from this viscosity change), the increase is about 80W in pump drive power.
The oil within the bearings is the primary source of frictional heat in this equation...
e.g.
www.mae.ncsu.edu/klang/courses/mae442/.../Journal%20Bearing.ppt
The oil within the bearings is the primary source of frictional heat in this equation...
e.g.
www.mae.ncsu.edu/klang/courses/mae442/.../Journal%20Bearing.ppt
Originally Posted By: supercity
Originally Posted By: Shannow
That's BITOG myth. Positive displacement pumps are simply that, and there's not enough variance to do that purely through heat transfer, and thinner oils have a higher internal pump leakage...
Common sense, maybe a BITOG myth, would suggest it is the higher oil pressure when using a higher viscosity lube that causes higher internal pump leakage. Is this not the case?
For any given viscosity, the thicker oil has less internal leakage. The pressure rises that we are talking here (small numbers of psi within 50 or 60 psi) are not going to counteract this.
Originally Posted By: Shannow
That's BITOG myth. Positive displacement pumps are simply that, and there's not enough variance to do that purely through heat transfer, and thinner oils have a higher internal pump leakage...
Common sense, maybe a BITOG myth, would suggest it is the higher oil pressure when using a higher viscosity lube that causes higher internal pump leakage. Is this not the case?
For any given viscosity, the thicker oil has less internal leakage. The pressure rises that we are talking here (small numbers of psi within 50 or 60 psi) are not going to counteract this.
Lesson to be learned.....thinner oils run cooler. Use the thinest oil your vehicle is spected for. Much better for your engine in the areas of start-up and lower temps at operating speeds.
Originally Posted By: mount
It would be a result of viscosity difference, but I don't think the different grade would affect temperature that much.
In theory though, a thinner oil flows better, transferring heat more effectively. This is consistent with the situation you described, but your temp change seems more drastic.
If that the case why is temp higher??? The heat should still be in the engine not in the oil...
It would be a result of viscosity difference, but I don't think the different grade would affect temperature that much.
In theory though, a thinner oil flows better, transferring heat more effectively. This is consistent with the situation you described, but your temp change seems more drastic.
If that the case why is temp higher??? The heat should still be in the engine not in the oil...
Originally Posted By: Shark
My previous two fills in the CTS-V have been with 5w30 G-Oil. I switched to 5w40 Rotella T6 and I didn't notice it right away but my hot oil temps went from a norm of about 201-203 degrees to 215-217. Is this a result of the weight difference, the additive package, or both possibly?
Gotta be. No other variables.
My previous two fills in the CTS-V have been with 5w30 G-Oil. I switched to 5w40 Rotella T6 and I didn't notice it right away but my hot oil temps went from a norm of about 201-203 degrees to 215-217. Is this a result of the weight difference, the additive package, or both possibly?
Gotta be. No other variables.
Rotella T6 5W-40 (HTHSV 4.0cP)is a much heavier oil than the specified M1 5W-30 (HTHSV 3.1cP) for the CTS-V.
So in addition to some of the reasons already mentioned you're oil pump is likely be in by-pass with the heavier oil at normal operating temp's, reducing the oil flow and thereby raising the oil temp's.
I suggest you dump the Rotella and run the spec' 5W-30 grade.
So in addition to some of the reasons already mentioned you're oil pump is likely be in by-pass with the heavier oil at normal operating temp's, reducing the oil flow and thereby raising the oil temp's.
I suggest you dump the Rotella and run the spec' 5W-30 grade.
What is the 5W-30 G-Oil's HTHSV??
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