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== American Petroleum Institute (API) Basestock Categories ==
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In a previous article I discussed the issue of "hydrocracked" or Group III
base oils vs. synthetic. I'd like to go a little more in depth with this
issue and discuss the actual refining methods used on petroleum basestocks
and how these methods affect the quality and classification of the basestocks.
First, understand that since 1993 basestocks have been classified by the API
(American Petroleum Institute) as one of 5 groups. The separation of Groups
1-3 (I - III) is based upon contamination and viscosity index (VI) of the
base. Groups IV (4) and V (5) are non-petroleum basestocks which are
classified by their type and not by their relative level of quality and/or
contaminant level.
You can download a PDF a copy of the categorization table below. Use it for
further reference as you go through this article:
http://TheMotorOilSite.com/downloads/06-17...zine-addons.pdf
GROUP I BASESTOCKS
Notice on the chart that Group I basestocks have a sulfur weight of greater
than .03% or 300 ppm. there is no upper cap so a Group I base could have
significantly higher levels of sulfur content (possibly up to 10 times higher,
or 3000 ppm, according to a Machinery Lubrication article - June 2003).
Also, from the chart you'll see that "Saturates" are less than 90%. This is
the useful portion of the base. The other 10%+ is made up of aromatic
compounds which are considered contaminants that are not beneficial to the
lubricating qualities of the base oil. The saturates level of some Group I
bases could be considerably lower than 90% which would leave the aromatic
content even higher (sometimes as high as 20% or more), lowering the
lubricating quality of the oil even further.
Group I base oils are solvent refined/dewaxed which is why their contaminant
levels are so high. The solvent refining/dewaxing processes are not nearly as
effective as hydro-treating/cracking/dewaxing processes.
Of course, the chart also shows that the VI of Group I base oils is pretty
low, ordinarily under 100, which allows for considerable change in viscosity
with temperature changes. Since you want the viscosity of your oil to remain
as consistent as possible over all temperatures you might encounter with your
vehicles and/or equipment, this is not a good thing.
Not to worry, though. It's highly unlikely that you would end up with a Group
I based motor oil in your engine as long as you make sure the oil meets/
exceeds the latest API specifications (SJ/SL for gas engines and CG-4, CH-4,
CI-4 for diesels). Group I oils simply can't pass the tests required to meet
these specs.
GROUP II BASESTOCKS
Group II basestocks, as shown by the chart, are of higher quality than Group
I bases and will thus have better performance characteristics. Group II oils
must have BOTH low sulfur (<= 0.03%) AND low aromatic (ie. high saturate: >=
90%) levels. If either requirement is not met, the base must be classified as
a Group I.
You'll see the VI requirement is the same for both Group I and Group II bases,
but in reality, Group II oils will nearly always have higher VI than Group I
bases simply because of the purification processes used to create Group II
oils.
Hydrocracking
At a bare minimum, to create a Group II basestock, hydrocracking will likely
be used to remove the majority of the sulfur and nitrogen impurities and to
convert aromatic compounds to non-aromatics which add to the lubricating
qualities of the base oil. Hydrocracking is a more severe form of
hydrotreating which is used to improve the oxidation stability and VI of the
base oil while lowering the pour point.
In both processes (treating and cracking) the base oil feed is passed over a
catalyst bed at high temperature and pressure. Hydrotreating will be done at
less than 650º F and under approximately 1000 psi pressure. Hydrocracking is
performed at higher temperature and pressure, so more pronounced molecular
reshaping occurs in hydrocracking. This results in fewer impurities in the
resulting basestock and better VI and pourpoint values.
However, the process is not nearly done when the hydrocracking is finished.
The base oil still needs to go through a dewaxing process to remove paraffins
that will negatively affect the base oil's cold temperature characteristics.
Hydroisomerization
So, Group II base oils will then be put through a dewaxing process called
hydroisomerization. This process is used in place of solvent and/or catalytic
dewaxing which are less effective/efficient and are more likely to be used at
older plants and/or those that are still producing Group I base oils.
Through the wax hydroisomerization process hydrogen is again used to convert
(isomerize) wax into high quality BRANCHED paraffin molecules which have very
good cold temperature characteristics (unlike the wax molecules that were
present before the isomerization process began). The isomerizing process is
less wasteful and produces higher yields and higher VIs than solvent and/or
catalytic dewaxing processes which are used for Group I base oils.
Hydrofinishing
As a final step toward "graduation" to a group II base oil, the base oil will
typically go through a final hydrofinishing phase where sophisticated
catalysts and extremely high pressures are used to remove the few remaining
impurities left in the base.
The final Group II base will be nearly colorless, will have very little
sulfur content and a high level of "Saturates" (useful lubricating compounds)
equal to or greater than 90% of the base oil (leaving 10% or less as
aromatics).
GROUP III BASESTOCKS
Now, on to the more controversial Group III basestocks that were discussed so
heavily in the last newsletter installment. First, let me apologize for being
in the habit of calling these basestocks "hydrocracks" or similar names. It's
a bad habit because, although they ARE hydrocracked oils, so are Group II
base oils, typically. So, from now on, I'll be sure to refer to these base
oils more correctly as simply Group III bases.
Very Similar To Group II
The only real difference between a Group II and Group III base oil,
technically speaking, is the higher viscosity index. This is the only
distinction made by the API Basestock Grouping System to differentiate the
two basestock groups.
In creating a Group III basestock there is also little difference from a
Group II base. The only difference is the original selection of the feed
stock (higher quality/higher VI crude oil for Group III) and/or the severity
of the hydrocracking process. Otherwise, the process is generally identical
for both basestock groupings.
Important to note (as I did in last month's article) is that "bumping" a base
oil's VI just one point (from 119 to 120) "converts" the base oil from a
Group II petro lube to a Group III synthetic. Nothing else has to change. In
fact, I'd be just about willing to bet that the ASTM D2270 viscosity index
test has enough margin for error that you could run it once and have a Group
II, 119 VI base oil on your hands, but if you ran it again you could end up
with a Group III, 120 VI base oil worth much more. Ironic, don't you think?
In light of this, as I've said before, it is entirely possible for a low
grade Group III "synthetic" base oil to perform only marginally better than a
high grade Group II petroleum base. Unfortunately, for the consumer,
synthetics typically command a premium price. So the very same low grade
Group III based motor oil that performs only marginally better than its high
quality Group II petro "cousin" will likely sell for about double the price,
putting a hefty profit into some oil company's "annual bonus fund".
Do You Really Know What's in That Bottle?
You just don't really know what you're getting anymore when you buy a quart
of motor oil. That's why I'm such a proponent of staying up to date and
comparing motor oil technical specifications. It's the only way to have any
reasonable assurance that you're buying an oil that's worth the price
you're paying for it.
WHY ARE GROUP III BASES SO POPULAR?
The reason that Group III basestocks have become so popular, in my opinion,
is three-fold. First, motor oil manufacturers realize that they can produce a
Group III "synthetic" oil for considerably less than a PAO based synthetic
while selling it for basically the same price as the PAOs.
Second, motor oil manufacturers recognize that their Group III synthetic
doesn't even HAVE to be a very high grade Group III in order to sell it as a
high priced synthetic oil, which creates even bigger profit margins.
Third, base oil suppliers recognized in the 90's that PAO bases were gaining
marketshare very quickly with nearly double digit growth each year for much
of the past decade. With more stringent motor oil specifications coming down
the pipe, Group II base oil producers knew they'd be facing even stiffer
competition from PAOs that could easily meet the specs.
Since the process for creating a Group III base is so similar to that of a
Group II, it only made sense for Group II plants to begin producing Group III
basestocks to compete with the growing PAO market. Great for the base oil
business and for motor oil manufacturers trying to save on manufacturing
costs while maintaining prices; bad for consumers, most of whom don't know
what they are buying and are getting the shaft.
It would be one thing if the savings created by designing synthetic oils with
Group III basestocks was being passed on to consumers, but it's not. When
Castrol switched it's Syntec product from a PAO base to a Group III, there
was no significant price change, even though you can bet Castrol was saving a
bundle on the cheaper basestocks. It might be great for profits, but it's
unfair to consumers.
WHY UNFAIR?
Some might say that I'm the one being unfair. It doesn't matter what the base
of a synthetic oil is, since Group III base oils can perform every bit as
good as a PAO base. However, I would contend that it is the difference
between "CAN" and "DO" that is so significant and causes the situation to be
unfair. The fact that a Group III base oil "CAN" be made to perform like that
of a PAO is really irrelevant. The question is, DO they typically perform as
well in the real world?
The point I'm trying to make is this. PAO basestocks (Group IV on the chart,
and traditionally considered "synthetic") contain NO sulfur and NO aromatic
compounds (though the chart doesn't indicate this). They are pure basestocks.
Also, although this isn't on the chart either, PAO basestocks typically have
a minimum VI of 145 and can even be considerably higher.
Group III basestocks, on the other hand, by definition, can have a VI as low
as 120, sulfur levels as high as 300 ppm and aromatic content as high as 10%
of the base. That means, even a low grade PAO would have a 20% higher VI than
a low grade Group III base, not to mention having considerably less sulfur
and aromatic content. Such an oil can't help but outperform a low grade Group
III base oil by a wide margin.
Also, recognize that the viscosity index of an oil only refers to the
relationship between viscosity change and temperature change of an oil
between 40 and 100º C (that's between 104 and 212º F). That's not a very wide
range. Often temperatures within an engine (and the oil itself) can rise
considerably higher than that. A PAO can easily handle such temperatures
without suffering a significant viscosity drop. Can a Group III oil? I'm not
so sure.
In addition, winter temperatures will often be as low as -20º to -40ºF in
some areas. The Viscosity Index score of an oil doesn't tell you what happens
to the viscosity of an oil as temperatures go WELL BELOW +40º C (104º F).
In fact, the graph at the following link is just a simple example of what can
happen to the viscosity of a VHVI (Very High Viscosity Index - Group III)
mineral oil as compared to a PAO when cold temperatures are encountered.
http://www.cpchem.com/pao/faqs/faq1.asp
Notice how the viscosity of the VHVI oil skyrockets as soon as the
temperature drops below 0º C (32º F). The viscosity of the PAO based fluid
(with an identical VI of 144) hardly moves until it hits about -40º C (-40º F)
. Which oil would you rather be using in your vehicle when temperatures drop
below the freezing mark?
THE LUBRICANTS INDUSTRY ISN'T DOING US ANY FAVORS
This isn't rocket science, folks. It's one thing to say that a Group III base
CAN be designed to perform as well as a PAO base, but it's quite another to
make it a reality in a cut throat lubricants industry that is already bilking
customers with unnecessary 3,000 mile oil changes.
These companies have made it very clear that their focus is on their bottom
line and NOT on the best interests of their customers. Just read any
lubricants journal which has interviewed top executives at these companies.
You'll see in about two seconds just how little they care about saving you
money, reducing unnecessary oil changes, reducing environmentally hazardous
oil disposal, protecting your vehicle, etc.
As long as their oil doesn't make your vehicle's engine blow up, what their
customers don't know won't hurt them. And, if it makes the company an extra
50 cents or a dollar per quart, what's the harm?
IT'S A SLAP IN THE FACE
This "open door" policy on Group III synthetic oils is a windfall for base
oil producers and motor oil manufacturers and a slap in the face to consumers
who are simply trying to make sure they are doing everything they possibly
can to protect their very expensive investments.

2003 BMW 325i
Dinan CAI, Throttle body
Dinan Exhaust
Dinan stage 3
Dinan Strut Braces

LPQuick, this is a fine Refinery 101 class mixed with a MBA 101 course to what purpose? You could change the text and talk about automakers use of plastics instead of metals in cars, or 100s of other cases where the manufacturer uses less than honest methods to trick retail customers.

To retail oil buyers know about space velocity in a hydrocraker catalyst bed? Only 600,000 MBA in the USA population of over 300 million. Most folks buy cars and change oil as recommended. Sure to us this is unfair. But to 99.99% this is just one of thousands of tricks we face daily.

Think of all the mutual fund and/or 401(k)/IRA tricks that happen under our noses.

Keep up the good work. My question is this: how does a retail buyer like me know for sure that my base oil is 100% PAO?