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Re: Synthetic Oil Filter for Cars

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@Mustang wrote:

As the VI improver breaks down it also gets too thin.


Does a VI improver always work in this direction as it breaks down, i.e., gets too thin? Or are there improvers that can get too thick when they break down? 

Added by edit: I just read that, "The addition of modifiers will only slow down the rate at which the viscosity decreases." here, so I think that answers it.

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Frequent Contributor

Re: Synthetic Oil Filter for Cars

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Multi-grade oils start with thin oil base to which polymers [VI improvers] are added that thicken the oil at higher temps. So, when these polymer additives deteriorate due to mechanical action or oxidation, oil becomes thin.

YBB
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Explorer ○

Re: Synthetic Oil Filter for Cars

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That is a good explanation of multi-grade oils. I like to explain it this way.  All oils will "thin out" as they are warmed up. The difference with multi-grade oils is with the addition of viscosity index (VI) improvers multi-grade oils will "thin out" at a much slower rate as the temperature increases. Think of it as the slope of a graph of viscosity vs. temperature. So, a 10w30 oil will act like 10 grade oil when cold (making cold starts easier) and like a 30 grade oil at high temperatures (thus protecting the engine). Hope this helps. 

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