All other factors being equal, might a used oil run warmer than fresh, new oil? Once the additive package and properties of the oil break down, will it no longer be able to dissipate heat as well and run at a higher operating temperature?
Does used oil run warmer?
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MolaKule
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It is primarily oxidation of the oil that thickens it.
Any oil that increases in viscosity will require more energy to move it, thereby raising its temperature slightly, but probably not measurable.
Any oil that increases in viscosity will require more energy to move it, thereby raising its temperature slightly, but probably not measurable.
dnewton3
Staff member
Originally Posted By: MolaKule
It is primarily oxidation of the oil that thickens it.
Any oil that increases in viscosity will require more energy to move it, thereby raising its temperature slightly, but probably not measurable.
I agree.
In theory, it most certainly has some effect.
In reality, you'd never be able to tell presuming the lube is still serviceable.
Obviously, a lube that is allowed to degrade so horrendously that it it more like Jello pudding than oil could probably see a minor tangible delta-T, but that's not what we do here on BITOG, right? In fact, I'd have to say that it's likely you'll never see the delta-T because most BITOGers OCI way too frequently.
And then we'd have to factor in the effects of the TCB (tribochemical barrier) that is promoted via heat oxidation, and actually HELPS reduce friction, as proven in SAE 2007-01-4133. Perhaps the reduction of friction off-sets the slightly thicker vis pumping energy resistance, and therefore the end result is a neutral effect? My point here is that you'd be darn hard pressed to be able to distinguish the internal variants and how they individually contribute in either direction.
The shift is so absurdly small (in either direction) that it makes for good breakfast fodder, but has no bearing on reality.
It is primarily oxidation of the oil that thickens it.
Any oil that increases in viscosity will require more energy to move it, thereby raising its temperature slightly, but probably not measurable.
I agree.
In theory, it most certainly has some effect.
In reality, you'd never be able to tell presuming the lube is still serviceable.
Obviously, a lube that is allowed to degrade so horrendously that it it more like Jello pudding than oil could probably see a minor tangible delta-T, but that's not what we do here on BITOG, right? In fact, I'd have to say that it's likely you'll never see the delta-T because most BITOGers OCI way too frequently.
And then we'd have to factor in the effects of the TCB (tribochemical barrier) that is promoted via heat oxidation, and actually HELPS reduce friction, as proven in SAE 2007-01-4133. Perhaps the reduction of friction off-sets the slightly thicker vis pumping energy resistance, and therefore the end result is a neutral effect? My point here is that you'd be darn hard pressed to be able to distinguish the internal variants and how they individually contribute in either direction.
The shift is so absurdly small (in either direction) that it makes for good breakfast fodder, but has no bearing on reality.
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Originally Posted By: dnewton3
And then we'd have to factor in the effects of the TCB (tribochemical barrier) that is promoted via heat oxidation, and actually HELPS reduce friction, as proven in SAE 2007-01-4133. Perhaps the reduction of friction off-sets the slightly thicker vis pumping energy resistance, and therefore the end result is a neutral effect?
You are talking a (misapplied) boundary effect paper versus fundamental physical rules of shear rate, viscosity and dimension. Viscosity effects remove the contact area from the boundary lubrication regime, so one would expect that the boundary friction reduction from used oil has a lessening effect as the viscosity increases...they don't cancel.
To the OP, used or new, the difference is probably comparable (or less) than changing brands...minuscule.
And then we'd have to factor in the effects of the TCB (tribochemical barrier) that is promoted via heat oxidation, and actually HELPS reduce friction, as proven in SAE 2007-01-4133. Perhaps the reduction of friction off-sets the slightly thicker vis pumping energy resistance, and therefore the end result is a neutral effect?
You are talking a (misapplied) boundary effect paper versus fundamental physical rules of shear rate, viscosity and dimension. Viscosity effects remove the contact area from the boundary lubrication regime, so one would expect that the boundary friction reduction from used oil has a lessening effect as the viscosity increases...they don't cancel.
To the OP, used or new, the difference is probably comparable (or less) than changing brands...minuscule.
dnewton3
Staff member
Originally Posted By: Shannow
Originally Posted By: dnewton3
And then we'd have to factor in the effects of the TCB (tribochemical barrier) that is promoted via heat oxidation, and actually HELPS reduce friction, as proven in SAE 2007-01-4133. Perhaps the reduction of friction off-sets the slightly thicker vis pumping energy resistance, and therefore the end result is a neutral effect?
You are talking a (misapplied) boundary effect paper versus fundamental physical rules of shear rate, viscosity and dimension. Viscosity effects remove the contact area from the boundary lubrication regime, so one would expect that the boundary friction reduction from used oil has a lessening effect as the viscosity increases...they don't cancel.
To the OP, used or new, the difference is probably comparable (or less) than changing brands...minuscule.
The OP asked if older oil runs warmer; to any practical degree, no. To a theoretical degree, possibly, but you'd have to consider ALL effects of ALL variables, and that would include the offset of the TCB, which is a proven phenomenon.
I will note that the study I reference specifically speaks to the wear reduction being directly attributed to the effect of the TCB and not the vis shift. Page 6, last paragraph, indicates that a 20% shift is vis did nothing to change the wear rate contrasting the two oils noted. Specifically, it was the chemical boundary layer. Similarly, the reduction of friction was noted as the TCB increased, and then stabilized, and was not attributed to the vis change; pages 6-8.
But the discussion is moot, IMO, because the shift in Vis and the effects of TCB are difficult to distinguish in terms of everyday thermal effect. It would be near impossible to prove that "old oil runs warmer" because the delta-T we'd be looking for would be obscured by other variables too difficult to control.
It makes for great fodder, as I said before. But it cannot be reasonably proven and it too difficult to separate the minutia of contributors. It's just idle BITOG banter and nothing more.
Originally Posted By: dnewton3
And then we'd have to factor in the effects of the TCB (tribochemical barrier) that is promoted via heat oxidation, and actually HELPS reduce friction, as proven in SAE 2007-01-4133. Perhaps the reduction of friction off-sets the slightly thicker vis pumping energy resistance, and therefore the end result is a neutral effect?
You are talking a (misapplied) boundary effect paper versus fundamental physical rules of shear rate, viscosity and dimension. Viscosity effects remove the contact area from the boundary lubrication regime, so one would expect that the boundary friction reduction from used oil has a lessening effect as the viscosity increases...they don't cancel.
To the OP, used or new, the difference is probably comparable (or less) than changing brands...minuscule.
The OP asked if older oil runs warmer; to any practical degree, no. To a theoretical degree, possibly, but you'd have to consider ALL effects of ALL variables, and that would include the offset of the TCB, which is a proven phenomenon.
I will note that the study I reference specifically speaks to the wear reduction being directly attributed to the effect of the TCB and not the vis shift. Page 6, last paragraph, indicates that a 20% shift is vis did nothing to change the wear rate contrasting the two oils noted. Specifically, it was the chemical boundary layer. Similarly, the reduction of friction was noted as the TCB increased, and then stabilized, and was not attributed to the vis change; pages 6-8.
But the discussion is moot, IMO, because the shift in Vis and the effects of TCB are difficult to distinguish in terms of everyday thermal effect. It would be near impossible to prove that "old oil runs warmer" because the delta-T we'd be looking for would be obscured by other variables too difficult to control.
It makes for great fodder, as I said before. But it cannot be reasonably proven and it too difficult to separate the minutia of contributors. It's just idle BITOG banter and nothing more.
Would that also imply that as an engine oil ages,
the wear rate may or may not change.
And if it did one way or another, it wouldn't be
enough to talk about if the total of 10 million
vehicles were added together.
Well that is good to know.
Now the subject of antagonistic
additives interfering with the anti wear additives
and friction modifiers can be dropped once and for all.
the wear rate may or may not change.
And if it did one way or another, it wouldn't be
enough to talk about if the total of 10 million
vehicles were added together.
Well that is good to know.
Now the subject of antagonistic
additives interfering with the anti wear additives
and friction modifiers can be dropped once and for all.
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