How to achieve “real-world” fuel economy gains from your viscosity modifier

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"Regarding extended shear stability, Fang compared an optimised OCP and an HSI star polymer. Both were put through extended shear cycles, and targeted to meet the same KV100 after 90-cycle shear in ASTM D7109, the Kurt Orbahn test. While both passed, the test was extended to 720 cycles, eight times the 90-cycle limit, at which point the linear optimised OCP had only sheared an additional 5%, as opposed to significant deterioration in the HSI structure after continuing the test beyond the current limits. Fang pointed out that "different chemistry really has an impact on shear stability." The optimised OCP demonstrated robust extended shear stability, retaining most of its architecture instead of breaking down. This can aid in supporting extended drain performance, he said."
 
JohnG said:
And how does this apply to the world I live in exactly?[/quot

I have never taken any courses in motor oil, but I think better sheer stable additives will allow the use of thinner oils that still provide the required thickness at the end of their oil change interval. Therefore allowing the use of thinner oils that get better MPGs.

In other words if you use only older additives that sheer a lot and become a lot thinner with use then the oil must be thicker initially so that when it is at the end of its useful life it is still thick enough to protect the engine. And because the amount of change of thickness (amount of sheering) is less with these modern better additives, then oils made with more sheer resistant additives can be designed to initially be thinner, and still provide enough thickness at the end of their oil change interval. And thinner oils mean less friction losses from pumping and moving parts pushing them out of the way, which results in better MPGs.

And an added big plus is that these additives thicken up less when cold, and therefore do not increase the pumping and friction losses when cold.
 
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Originally Posted by JimPghPA
... And an added big plus is that these additives thicken up less when cold, and therefore do not increase the pumping and friction losses when cold.
Good post, mostly, but you're forgetting that pumping losses are trivial, compared to drag caused by shearing oil elsewhere.
 
The OCP—olefin copolymer—VII is definitely the VII to go in gasoline-engine applications, as it runs clean, which is important for turbochargers etc. The hydrogenated styrene star VII runs dirty, but it's popular in heavy-duty diesel engine applications because of higher permanent shear stability, as maintaining the viscosity is critical for these applications. However, the extended-cycle shear tests in the article in the original post put it to shame, and it looks like there is really no advantage of using a star VII in any engine-oil application, and the VII selection for engine-oil applications pretty much boils down to optimizing the OCP VII.

There is also the PMA—poly(methyl acrylate)—VII, particularly the comb type, used by the Japanese OEM's in some ultra-high-VI engine-oil applications, but they are the dirtiest-running VII's by far, as they require an extremely high solid-polymer treat rate.
 
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oils + their formulations surely vary + are quite complicated!! good reading for sure
 
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