There seems to be a missing link when comparing engine oils containing VII/VMs in escalating treatment levels with each other and to mono-grade engine oils.
Mono-grade engine oils as a group, have higher densities than the above mentioned conventional VII/VM containing multi-grade engine oils.
The mono-grades, as a group have higher HTHS for a given KV100 specification than VII/VM containing engine oils.
When comparing VII/VM conventional multi-grades with each other, the densities go down with increased viscosity grade spread,
which could be attributed to higher VII/VM treatment levels.
With the resulting density being lower from the VII/VMs, the relationship between KV100 and HTHS suffers.
Often when comparing a series of multi-grade engine oils from a manufacture, for example brand XYZ 0W20, 0W30 and 0w40 will have descending densities, along with corresponding worsened KV100 vs. HTHS values.
Is there an explanation for the non-linear relationship between density, VI and HTHS?
Another stumbling block, is the temporary shear that VII containing engine oils experience in the bearing space at high journal speeds, which in turn produce high shear rates.
The temporary shear in addition to the reduced HTHS of a VII/VM containing engine oil should be a factor when choosing the right product for the application.
It seems to me that many people are buying an engine oil based on it's VI and cold flow attributes, while overlooking the reduced HTHS those lubricants may exhibit for a given KV100 specification.
Mono-grade engine oils as a group, have higher densities than the above mentioned conventional VII/VM containing multi-grade engine oils.
The mono-grades, as a group have higher HTHS for a given KV100 specification than VII/VM containing engine oils.
When comparing VII/VM conventional multi-grades with each other, the densities go down with increased viscosity grade spread,
which could be attributed to higher VII/VM treatment levels.
With the resulting density being lower from the VII/VMs, the relationship between KV100 and HTHS suffers.
Often when comparing a series of multi-grade engine oils from a manufacture, for example brand XYZ 0W20, 0W30 and 0w40 will have descending densities, along with corresponding worsened KV100 vs. HTHS values.
Is there an explanation for the non-linear relationship between density, VI and HTHS?
Another stumbling block, is the temporary shear that VII containing engine oils experience in the bearing space at high journal speeds, which in turn produce high shear rates.
The temporary shear in addition to the reduced HTHS of a VII/VM containing engine oil should be a factor when choosing the right product for the application.
It seems to me that many people are buying an engine oil based on it's VI and cold flow attributes, while overlooking the reduced HTHS those lubricants may exhibit for a given KV100 specification.
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