Looking at different UOA and in cases that the oil shears down a grade or more the comments are usually "Your oil went from a 30 weight to a 20 weight." So the question I have is what happens to the first number like it was a 10w30 so now is it a 5w20 or a 0w20? How much does the first number change?
Oil shear and 0w,5w,10w?
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Seems like it's generally worse at higher temps, so it would be a decrease in the 2nd number. The viscosity improvers get sheared by bearings & timing chains, therefore the hot viscosity starts resembling the low W number, i.e. your 10W30 gradually becomes a 10W20.
Originally Posted By: Camprunner
... How much does the first number change?
Not much, I suspect, because it depends mainly on low-temperature properties of the base oil, which isn't affected by the shearing of VI improvers.
... How much does the first number change?
Not much, I suspect, because it depends mainly on low-temperature properties of the base oil, which isn't affected by the shearing of VI improvers.
Originally Posted By: fdcg27
FWIR, the current API standard allows any 0W to slip to a 5W in service.
...
So? Camprunner's question had to do with shearing, not oxiditive thickening.
FWIR, the current API standard allows any 0W to slip to a 5W in service.
...
So? Camprunner's question had to do with shearing, not oxiditive thickening.
Originally Posted By: Dyusik
Poor point depressants are large molecules iirc, they surely shear as the vii do. One thing for sure, oxidative thickening will play a role.
You're correct that PPDs are large polymeric molecules (usually Poly-Methacrylates) but they generally DON'T shear down. They typically have a lower molecular weight than VIIs and would classify as zero SSI on the Bosch KO30 shear rig. I only know this because several years ago I was looking for a PPD which WAS easily shearable and most disappointed to discover they didn't!
Poor point depressants are large molecules iirc, they surely shear as the vii do. One thing for sure, oxidative thickening will play a role.
You're correct that PPDs are large polymeric molecules (usually Poly-Methacrylates) but they generally DON'T shear down. They typically have a lower molecular weight than VIIs and would classify as zero SSI on the Bosch KO30 shear rig. I only know this because several years ago I was looking for a PPD which WAS easily shearable and most disappointed to discover they didn't!
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Originally Posted By: SonofJoe
Originally Posted By: Dyusik
Poor point depressants are large molecules iirc, they surely shear as the vii do. One thing for sure, oxidative thickening will play a role.
You're correct that PPDs are large polymeric molecules (usually Poly-Methacrylates) but they generally DON'T shear down. They typically have a lower molecular weight than VIIs and would classify as zero SSI on the Bosch KO30 shear rig. I only know this because several years ago I was looking for a PPD which WAS easily shearable and most disappointed to discover they didn't!
Thanks for sharing that.
Originally Posted By: Dyusik
Poor point depressants are large molecules iirc, they surely shear as the vii do. One thing for sure, oxidative thickening will play a role.
You're correct that PPDs are large polymeric molecules (usually Poly-Methacrylates) but they generally DON'T shear down. They typically have a lower molecular weight than VIIs and would classify as zero SSI on the Bosch KO30 shear rig. I only know this because several years ago I was looking for a PPD which WAS easily shearable and most disappointed to discover they didn't!
Thanks for sharing that.
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Originally Posted By: Camprunner
Looking at different UOA and in cases that the oil shears down a grade or more the comments are usually "Your oil went from a 30 weight to a 20 weight." So the question I have is what happens to the first number like it was a 10w30 so now is it a 5w20 or a 0w20? How much does the first number change?
While the 2nd number is based on KV100, which is generally achieved with Viscosity Index Improvers, the first number is based on CCS and MRV performance, which is achieved via base oil selection and viscosity as well as Pour Point Depressants.
So, when an oil is in service, you have a few things going on, which include, but are not limited to:
- Oxidation
- Shearing
- Contaminant suspension
The first two run contrary to each other. That is, while the mechanical action of engine components on the VII's works to break them and reduce viscosity, as the oil oxidizes, it thickens. Generally, we only see that on longer run UOA's on here, which means we don't see it frequently
The last one also can lead to thickening, but it depends on what the contaminants we are discussing are. Fuel is a contaminant, that gets into the oil that thins it out, reduces its flashpoint and may actually aide in cold temperature performance, whilst carbon particulate and other contaminants will make it thicker.
As Shannow mentioned, an oil is allowed to slip a W rating in service, so the W number generally heads the opposite direction of the KV100 number. So you have your multi-grade working to head for straight-weight territory.
Now, certain base oils have better natural VI's than others. A PAO can do 5w-20 or 10w-30, perhaps even a 0w-20. And shear is not the only cause of viscosity loss as I touched on earlier. Often what is ascribed to shear on here ignores the flashpoint, which will point to fuel being a player as well. A PAO-based synthetic will not need the volume of PPD's (due to the absence of wax) that a lesser group base will in order to achieve cold temperature performance. And this means you can start with a heavier PAO than you would say a Group II, so the latter would need more VII's to hit the KV100 target than the former.
So it depends on a number of things but if we were looking to generalize, I would say that the W rating has a loosely inverse relationship to the KV100 SAE grade in service. As the VII's shear and the fuel dilutes, the overall viscosity drops, but this is competing with oxidative and contaminant thickening which works to bring viscosity back up. The oxidized product will not have the same cold temperature performance as the original blend. So you end up with a narrower and narrower spread as time goes on. A synthetic oil will be more resistant to this phenomena, particularly one with a lot of PAO in the base blend.
Looking at different UOA and in cases that the oil shears down a grade or more the comments are usually "Your oil went from a 30 weight to a 20 weight." So the question I have is what happens to the first number like it was a 10w30 so now is it a 5w20 or a 0w20? How much does the first number change?
While the 2nd number is based on KV100, which is generally achieved with Viscosity Index Improvers, the first number is based on CCS and MRV performance, which is achieved via base oil selection and viscosity as well as Pour Point Depressants.
So, when an oil is in service, you have a few things going on, which include, but are not limited to:
- Oxidation
- Shearing
- Contaminant suspension
The first two run contrary to each other. That is, while the mechanical action of engine components on the VII's works to break them and reduce viscosity, as the oil oxidizes, it thickens. Generally, we only see that on longer run UOA's on here, which means we don't see it frequently
As Shannow mentioned, an oil is allowed to slip a W rating in service, so the W number generally heads the opposite direction of the KV100 number. So you have your multi-grade working to head for straight-weight territory.
Now, certain base oils have better natural VI's than others. A PAO can do 5w-20 or 10w-30, perhaps even a 0w-20. And shear is not the only cause of viscosity loss as I touched on earlier. Often what is ascribed to shear on here ignores the flashpoint, which will point to fuel being a player as well. A PAO-based synthetic will not need the volume of PPD's (due to the absence of wax) that a lesser group base will in order to achieve cold temperature performance. And this means you can start with a heavier PAO than you would say a Group II, so the latter would need more VII's to hit the KV100 target than the former.
So it depends on a number of things but if we were looking to generalize, I would say that the W rating has a loosely inverse relationship to the KV100 SAE grade in service. As the VII's shear and the fuel dilutes, the overall viscosity drops, but this is competing with oxidative and contaminant thickening which works to bring viscosity back up. The oxidized product will not have the same cold temperature performance as the original blend. So you end up with a narrower and narrower spread as time goes on. A synthetic oil will be more resistant to this phenomena, particularly one with a lot of PAO in the base blend.
Originally Posted By: SonofJoe
You're correct that PPDs are large polymeric molecules (usually Poly-Methacrylates) but they generally DON'T shear down. They typically have a lower molecular weight than VIIs and would classify as zero SSI on the Bosch KO30 shear rig. I only know this because several years ago I was looking for a PPD which WAS easily shearable and most disappointed to discover they didn't!
This really got my attention...are you at liberty to discuss your desire for a shearable PPD?
You're correct that PPDs are large polymeric molecules (usually Poly-Methacrylates) but they generally DON'T shear down. They typically have a lower molecular weight than VIIs and would classify as zero SSI on the Bosch KO30 shear rig. I only know this because several years ago I was looking for a PPD which WAS easily shearable and most disappointed to discover they didn't!
This really got my attention...are you at liberty to discuss your desire for a shearable PPD?
Originally Posted By: Virtus_Probi
Originally Posted By: SonofJoe
You're correct that PPDs are large polymeric molecules (usually Poly-Methacrylates) but they generally DON'T shear down. They typically have a lower molecular weight than VIIs and would classify as zero SSI on the Bosch KO30 shear rig. I only know this because several years ago I was looking for a PPD which WAS easily shearable and most disappointed to discover they didn't!
This really got my attention...are you at liberty to discuss your desire for a shearable PPD?
It's ancient history now and my 'desire' is all but spent! However if you type the words 'sacrificial viscosity improver' into Google, you might just find a patent that reveals all.
Originally Posted By: SonofJoe
You're correct that PPDs are large polymeric molecules (usually Poly-Methacrylates) but they generally DON'T shear down. They typically have a lower molecular weight than VIIs and would classify as zero SSI on the Bosch KO30 shear rig. I only know this because several years ago I was looking for a PPD which WAS easily shearable and most disappointed to discover they didn't!
This really got my attention...are you at liberty to discuss your desire for a shearable PPD?
It's ancient history now and my 'desire' is all but spent! However if you type the words 'sacrificial viscosity improver' into Google, you might just find a patent that reveals all.
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Originally Posted By: CR94
Originally Posted By: fdcg27
FWIR, the current API standard allows any 0W to slip to a 5W in service.
...
So? Camprunner's question had to do with shearing, not oxiditive thickening.
Read Camprunner's post, not just the thread title.
Originally Posted By: fdcg27
FWIR, the current API standard allows any 0W to slip to a 5W in service.
...
So? Camprunner's question had to do with shearing, not oxiditive thickening.
Read Camprunner's post, not just the thread title.
Originally Posted By: fdcg27
FWIR, the current API standard allows any 0W to slip to a 5W in service.
It isn't the base oil alone that determines the winter qualification of an oil.
does this mean a 0W oil can never become a 10W in order to pass API standard?
just curious, how is this "service allowance" defined and/or tested/evaluated?
so many variables here when it gets to consumer, engine type, temp, etc. ...
FWIR, the current API standard allows any 0W to slip to a 5W in service.
It isn't the base oil alone that determines the winter qualification of an oil.
does this mean a 0W oil can never become a 10W in order to pass API standard?
just curious, how is this "service allowance" defined and/or tested/evaluated?
so many variables here when it gets to consumer, engine type, temp, etc. ...
Last edited:
Originally Posted By: OilUzer
Originally Posted By: fdcg27
FWIR, the current API standard allows any 0W to slip to a 5W in service.
It isn't the base oil alone that determines the winter qualification of an oil.
does this mean a 0W oil can never become a 10W in order to pass API standard?
just curious, how is this "service allowance" defined and/or tested/evaluated?
so many variables here when it gets to consumer, engine type, temp, etc. ...
It's in the Standard engine tests, and the bench oxidation test that the "used" oil sample is obtained from
http://www.aftonchemical.com/Afton/media/PdfFiles/Specification_Handbook.pdf (page 33 in browser window).
In YOUR engine, YOUR OCI, and YOUR driving style, YMMV.
Originally Posted By: fdcg27
FWIR, the current API standard allows any 0W to slip to a 5W in service.
It isn't the base oil alone that determines the winter qualification of an oil.
does this mean a 0W oil can never become a 10W in order to pass API standard?
just curious, how is this "service allowance" defined and/or tested/evaluated?
so many variables here when it gets to consumer, engine type, temp, etc. ...
It's in the Standard engine tests, and the bench oxidation test that the "used" oil sample is obtained from
http://www.aftonchemical.com/Afton/media/PdfFiles/Specification_Handbook.pdf (page 33 in browser window).
In YOUR engine, YOUR OCI, and YOUR driving style, YMMV.
Originally Posted By: SonofJoe
It's ancient history now and my 'desire' is all but spent! However if you type the words 'sacrificial viscosity improver' into Google, you might just find a patent that reveals all.
btw, nice job with the patent!!!
It's ancient history now and my 'desire' is all but spent! However if you type the words 'sacrificial viscosity improver' into Google, you might just find a patent that reveals all.
btw, nice job with the patent!!!
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