[BiturboS4] engine oils

Lance Fisher lfisher at cyberoptics.com
Thu Sep 12 12:24:13 EDT 2002

California Fields wrote:

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>I did some research over the weekend to try and find out more info about
>engine oils. To my dismay, there is still quite a bit of conflicting
>information out there. Still, I tried to put together what seemed consistent
>and logical.  I thought you might be interested in what I found (some may seem
>common sense but I figured it would be good to cover all bases). I apologize
>for the long post but thought it would be useful.
>Engine oil is made primarily from a "base stock" and an "additive package" to
>enhance the positive qualities of the oil and reduce the negative ones.  There
>are two types of basestocks, petroleum (refined from crude oil) and synthetic
>(created from pure compounds).  However, recently oil companies have created
>psuedo-synthetics (oils that are labeled as synthetic even though they
>originate as crude oil) because they are highly purified crudes (have very
>little contaminants) and do not resemble basic petroleums.  This labeling is
>legal and so you have to be aware that synthetic doesn't necessarily mean that
>the oil had been engineered from pure compounds.  Therefore, there are really
>three categories (petroleum, synthetic, and psuedo-synthetic).
>The imporant thing about oil is that it should satisfy all of your engine's
>requirements: lubrication, heat dissipation, cleaning (removal of deposits),
>and protect against oxidation and other corrosion.  Now, although all
>basestocks can provide each of these requirements, they don't meet the high
>stringincies of today's engines and so additives must be included to make up
>for the difference.  It's really the type and amount of additives that make
>engine oils different from each other because the basestocks used today are
>very similar (within each category - petroleum and synthetic).  The important
>thing to recognize here is that synthetic basestocks are inherently better at
>meeting the engine's requirements than petroleum basestocks and so the
>synthetic basestocks need less additives.  The question that I wasn't able to
>find an answer for is whether more additives = higher probablity of oil
>So, I read some more and found that, basically, you have to look at all the
>objective data available on the oil (viscosity index, flash point, pour point,
>etc.) and compare these data points between oils.  The one that scores the
>best in each category will be the best oil. Unfortunately, there isn't an oil
>that is consistently best in each category and so you have to choose which
>category is most important to your engine's needs.  I will spend some time
>putting together the names of all of these categories, their explanations, and
>what numbers you should look for.  Hopefully I'll have time this week.
>One thing to keep you interested is that the Amsoil 0W30 and 5W30 were rated
>the best when you compare the objective categories (they had the best
>numbers).  More later...


One thing you haven't touched on is the issue of Viscosity Index (the
ratio of viscosity decrease to temperature increase) and VI "improvers".
 My understanding is that synthetic based motor oil has a higher VI than
any crude base (don't know anything about the base of "psuedo synth").
 In order to bring the VI up to the levels needed for 10W30 or 10W40 the
motor oil manufacturers add special long chain hydrocarbon molecules to
the mix.  These compounds coil up into short "chunks" when cold and
unwind into long "strings" when hot.  The longer the molecules become
the more they increase the viscosity of the base oil.  There are two
issues with this.  One is that over time the long chains get sheared
into shorter chains resulting in a loss of VI.  The other is that there
is AFaIK some suspicion that while VI improvers do indeed make the oil
more viscous at elevated temps they may not actually cause the base oil
to lubricate (prevent metal to metal contact) any better at high temps
than the same oil would do without the VI improver.  In other words from
a pure lubrication perspective the petro based 10W40 may be no better at
protecting cylinders and bearings than a straight 10 weight oil at high
temps.  The VI improvers do prevent the loss of oil pressure at high
temps that would otherwise occur if a straight 10 weight petro based oil
was used so there is definitely some benefit but since synthetics have
an inherently higher VI and little or no VI improver is needed to
produce a 10W30 or  5W30 these concerns are minizmized.

I've also been told many times that synthetic based oil carbonizes at a
much higher temp than dino juice.  I don't really know if this is true
or just an OWT but based on what I have heard I believe it to be true.
 I wonder where the psuedo synthetics are in this regard?


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