Quote:
My guess is that those high VI lubricants that do not need VII to achieve a multi-grade classification, but contain some sort of additive that acts like a VII. That new additive is quite likely sacrificed, sheared or lost in translation over the duty cycle of the lubricant.
They do NOT have to contain another additive.
Let's take Amsoil ACD for example:
http://www.amsoil.com/shop/by-product/mo.../?code=ACD1G-EA
It is a 30W/10W30 because of the base oil viscosity mix.
I am not saying these are Amsoil's formulation(s) but merely using these ratios below to prove a point.
A base oil is NOT one Single viscosity of base oil as I have explained many times here.
A formulator can take a binary blend (a blend of two base viscosities), or a ternary (a blend of three base viscosities), or an n-ary (a blend of "n" viscosities where n is any number) to make a base mix oil behave any way he desires.
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For example a 5W30
PAO 4 14%
PAO 20 56%
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A 5W40
PAO 4 20%
PAO 6 48%
PAO 65 2%
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A 10W30/30
PAO 6 25%
PAO 8 44%
PAO 150 1%
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Here's the main point:
By introducing
a low percentage of high viscosity base oil (which would have a high Viscosity Index and a relatively high HTHS), one can make a mono-grade oil that also behaves as a multi-grade oil.