Originally Posted By: Virtus_Probi
Originally Posted By: kschachn
This is a common sentiment and statement on here but one that really isn't supported by any facts as far as I've seen. I wouldn't suppose that all VII additives are similar and I don't think there is any evidence that anyone who uses a 0W-40 oil is experiencing "a bit more engine wear". There's no indication that is happening is there?
Is there any readily available test that conclusively shows that a viscosity decrease is due to shearing as opposed to fuel dilution?
Originally Posted By: Virtus_Probi
It gets a little complicated when you're looking at a wide "spread" oil like a 0W40, as the maker might have to use a heavy dose of Viscosity Index Improver (VII) additives that can shear (temporarily or permanently) in operation and result in a lower viscosity and minimum film thickness when hot. Because of this, it is often recommended to use oils that are thicker at low temp when you don't experience cold temperatures in your area...if you're in Florida or South Texas, maybe use a 10W30 instead of 0W30. It seems that the use of good synthetic base stocks can allow 5W20 and 10W30 oils to be made with no VIIs and those oils can be expected to be especially resistant to shear.
Of course, plenty of people use 0W40 oils in warm climates with no problems. You just might be getting a bit more engine wear in a warm place due to what it takes to make the oil work well at extreme cold, and that cold performance isn't even buying you anything.
My memory is that Shannow posted some really good graphs from studies on this topic. It would take me forever to track them down and I'm hoping that he might see this and save me here! I might be able to search more later tonight, but I'm not completely sure the thread involved even started off with the discussion of VIIs.
It's also quite likely that I misremembered and/or misunderstood and am completely full of it. As I have mentioned elsewhere, I would very happy to switch from 5W30 to 0W30 if I didn't lose in NOACK performance and LSPI resistance as a result...the prospect of extra VIIs in the oil wouldn't be a big concern for me.
I did manage to find this from Oronite...
https://www.oronite.com/paratone/calcviscosity.aspx
Originally Posted By: kschachn
This is a common sentiment and statement on here but one that really isn't supported by any facts as far as I've seen. I wouldn't suppose that all VII additives are similar and I don't think there is any evidence that anyone who uses a 0W-40 oil is experiencing "a bit more engine wear". There's no indication that is happening is there?
Is there any readily available test that conclusively shows that a viscosity decrease is due to shearing as opposed to fuel dilution?
Originally Posted By: Virtus_Probi
It gets a little complicated when you're looking at a wide "spread" oil like a 0W40, as the maker might have to use a heavy dose of Viscosity Index Improver (VII) additives that can shear (temporarily or permanently) in operation and result in a lower viscosity and minimum film thickness when hot. Because of this, it is often recommended to use oils that are thicker at low temp when you don't experience cold temperatures in your area...if you're in Florida or South Texas, maybe use a 10W30 instead of 0W30. It seems that the use of good synthetic base stocks can allow 5W20 and 10W30 oils to be made with no VIIs and those oils can be expected to be especially resistant to shear.
Of course, plenty of people use 0W40 oils in warm climates with no problems. You just might be getting a bit more engine wear in a warm place due to what it takes to make the oil work well at extreme cold, and that cold performance isn't even buying you anything.
My memory is that Shannow posted some really good graphs from studies on this topic. It would take me forever to track them down and I'm hoping that he might see this and save me here! I might be able to search more later tonight, but I'm not completely sure the thread involved even started off with the discussion of VIIs.
It's also quite likely that I misremembered and/or misunderstood and am completely full of it. As I have mentioned elsewhere, I would very happy to switch from 5W30 to 0W30 if I didn't lose in NOACK performance and LSPI resistance as a result...the prospect of extra VIIs in the oil wouldn't be a big concern for me.
I did manage to find this from Oronite...
https://www.oronite.com/paratone/calcviscosity.aspx
