MR RICHARD T TRENK SR wrote (in part):
>While speaking to any of the oil co's be sure to ask about Viscosity Index
>(VI) numbers and how this relates to oil film strength and resistence to
>penetration of the hydranamic wedge when VI fails to stand up.
>The interesting thing about VI (which has no relation to oil viscosity) is
>that Pennsylvania crude has the highest natural number ( about 114 I
>recall?) and when they refine it they have to purchase and add the "least"
>amount of VI-Improvers, which are expensive.
>The Penn. oils could technically be sold cheaper than any other oil in the
>world because it costs less to make the finished product.
>Does this happen????? hell no ! Quaker State, Pennzoil and other Penn. base
>oils always are amongst the highest in cost to the public because they hype
>their name for 90 years. The lower grade crude oils, like Mid-continent,
>LaBrea, Gulf grade etc. are quite a bit more costly to mfr. due to more
>additives being needed in order to meet the the SAE and API specs.
>Fact is, that all SH rated oils must and do perform the same! Throughout
>the years that the API has provided their ratings, this equality has been
When I took my "Fuels and Lubricants" class (probably many decades after
Dick T.) my instructor said that the *definition* of 100 for the viscosity
index was the change of viscosity with temperature exhibited by the
grade oils, and 0 was the change of viscosity exhibited by the Gulf Coast
oils. This certainly was borne out by the VI tests that we made in the lab.
My instructor's point was that *all* oils have very significant changes
of viscosity with temperature -- and that politics can be used to define
the standards by which we judge something as excellent or poor.
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