Viscosity Index

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Pennzoil conventional has a VI of 150 vs. Motorcraft Syn. Blend of 164. This according to latest PDS. Given a higher VI would have flow better over a range of temperatures, what advantage does Motorcraft have over Pennzoil, if any. I believe Pennzoil is group 11+ am MC is group 11+ and group 3. This is 5w-20 weights.
 
Originally Posted By: RedOak
Given a higher VI would have flow better over a range of temperatures


How do you figure that ?
 
You need to know exact viscosity of each at several temperatures because there's a range of approved thickness at for example 100C, even though its narrower at 5w20, still cold cranck, mrv tests, hths tests, etc...
 
The VI simply is how the viscosity changes from cold to hot. But!!! there is the base oil viscosity index and the finished oil Viscosity index. It is more complicated, but my simple mind.
 
Simple Minds, ahh great band, but but, the one thing I do know about Viscosity Index is that there is an inverse relationship with it and HT/HS, namely as VI goes up, the HT/HS plummets like a rock, atleast here on this site.
 
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VI is simply a calculated value based on 40C and 100C measured viscosity. It allows one to extrapolate in between and away from those points, but begins to lose relevance once you delve below 0C.

A higher VI oil will be closer to operating viscosity during start and warm-up than one with a lower VI. This has a minuscule effect on fuel economy due to pumping losses. However a high VI oil doesn't not mean it will flow better in extreme cold conditions where the relevance of flow actually becomes important. That's why there are the two cold temperature performance metrics: CCS and MRV, which measure cold temperature effect on cranking speed (CCS) and the pumping viscosity (MRV).

Ergo, VI isn't about "flow" as much as it is about trying to get as close to operating (optimal) viscosity as possible during the warm-up phase, which is where the biggest fuel economy penalty takes place.

An example, Mobil 1 EP 0w-20 has probably the best CCS and MRV on the market, meaning it is the thinnest at -35C and -40C respectively, yet it does not have a "stratospheric" VI. Because VI doesn't correlate to extreme cold temperature performance.
 
Originally Posted By: RedOak
Thanks for the input ole Shannow. Asked some questions and you screw the thread. Good job


Not "screwing the thread" for your questions, just how do you correlate viscosity index and flow ?

These the two PDS ???

https://www.fcsdchemicalsandlubricants.c...tic%20Blend.pdf

http://www.pennzoil.com/en_us/products/b...0-Motor-Oil.pdf


You can plug them into the Widman charting tool
http://www.widman.biz/English/Calculators/Graph.html

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Clearly, so close as to be indifferentiable in terms of viscosity and typical versus actual specs...and as to difference in "flow", in an operating engine...ummm, that was actually YOUR statement, which I asked you to justify.

Between 40C, 100C, and past 100C, the lower viscosity index oil will (according to your premise) "flow" more, clearly.

Back to your questions about the other advantages of the MC 5W-20, as per the data sheets.

It's got a massive flashpoint of 206C, versus the Pennz regular of only...ermm wait, 229C.

Well there's the CCS...hmm, that's the same.

Pour point ? well one is -42, one is < -42.

But yes, one has higher viscosity index
 
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