Guide to base oils

Base Oils
Types, classification,
Nomenclature
And queries
M Hussam Adeni
Chemical Engineer by education
Lubricant Specialist by Certification Experience and Membership
 Certification - MLA 1 – www.icml.com - (Lube Council)
 Experience – Castrol, BPCastrol
 GHG mitigation and Fuel Conservation Evangelist byPhilosophy
https://www.linkedin.com/in/hussamadeni/
https://twitter.com/hussamadeni
hussam_adeni@yahoo.com Lubricant Specialist & Tribologist
hussam.adeni@gmail.com What’s App: +966560706429

To start a discussion on Base Oils, it is important to know the source and the basics of raw material used, in
a Lubricant. Mobil - Engine Oil Fundamentals (weblink posted below) pictorially depicts the basics below:
Source:
https://club.mobilindustrial.com/lube_talk/b/product_and_application_expertise/posts/engine-oil-
fundamentals-part-1-back-to-basics-with-base-oils-in-engines

#1
Base Oils, what are the typical “Cp, Cn, Ca” or carbon numbers?
According to Organic Chemistry Reactions for Crude oil Products, Lube Oil base stocks are obtained from Heptadecane (C12H36)
and Octadecane (C18H38), as depicted pictorially below:
Citing from Valero - Distillation Units and Fractions

#2
How much Base Oil is obtained from a barrel of Crude Oil?
Base oil is produced through the refining – fractional distillation under vacuum- of crude oil. A 42-gallon barrel of crude oil can
actually yield nearly 45 gallons of petroleum products, but only about 0.4 gallons or less than 1% yield is Base Oil, the building
block for lubricants. The bulk goes to gasoline, diesel fuel and kerosene-type jet fuels. In view of the low yield, Lubes are a prized
commodity. In view of the limited supply, reusing and re refining used lube oil needs has merits.
Another view sourced from a Péter NÉGELI,MOL ppt.

A recent study on the use of base oils today shows, that Group II base oils, are the most commonly used base oils making up, 47
percent of the capacity. Compared to 21percentforbothGroupIIandIIIbaseoils, justa decade ago. Currently, Group III
accounts for less than 1 percent of the capacity in plants. Group I base oils previously made up 56 percent of the capacity,
compared to 28 percent of the capacity in today’splants.
#3
What is the Hydrocarbon composition in Base Oils?
Firstly, Base Oils are generally of three types:
i) Paraffinic Base stocks,
ii) Napthenic Base stocks and
iii) Aromatics Base Stocks.
The source/geographical region and location of the oil decides, if base Oil is Paraffinic or Napthenic. Very much like the “sweet
crudes” and “sour crudes.” However, most oils across the world are Paraffinic in nature. There are pockets in the Scandinavian
countries (Sweden – brand Nynas) and also in the US (Louisiana crudes rather than, Pennsylvania crudes – brands Calumet,
Ergon), where the oils are Napthenic in nature.
Base Oils are generally classified by the Carbon content, designated under Paraffinic (Cp), Napthenic (Cn), Aromatic (Ca),
content. The typical Carbon type analysis will show (Paraffins-Cp=65,NapthenicCn=34.5,AromaticsCa=0.5). As most of the
crudes are Paraffinic in nature hence, refining or distillation of this base stock, will yield only paraffinic grades. Typically,
distillation will strip paraffins/wax, aromatics etc. Resulting in a product that is “Paraffinic” in nature
Most Base oil available around the world are Paraffinic, as above. These have wide application and typically most Lubricants
are Paraffinic in nature and is the preferred base stock. These can be classified as Group I, II ( for Hydro treated), III (for
Hydrocracked).
Due to the limited availability of Napthenic base oils, from time to time, we hear claims “offering Naphthenic Base stocks”
from sources, other than, Scandinavian or US. Needless to say, such claimants would be potential candidates for “Nobel prize.”
To add to the confusion, the Distillation Technology providers, refer to components of the distillation yield, in PNA
terms, as
 n-P,
 i-P,
 Naphthenes
The PNA represents the (Carbon composition or spread for Ca, Cp, Ca) values for the different distillation yield/Cuts.
The use of an archaic term “Napthene” in the yield confuses Distillation Industry professionals, who fall prey and cite their
product to be a “Napthenic Base Oil”. In reality, none of the unique Napthenic Base Oils features,like
 Atomic Carbon composition for Napthenic (Cn = 45)
 Aniline Point (63 to 84range)
meet the qualifying benchmark. It is unlikely, that feedstock that is a Paraffinicbase (likeDiesel,Kerosene) can get
converted to Napthenic Base Oil, during a distillationprocess.
While deploying selective catalytic processes, it may, just be possible, to convert Paraffinic to Napthenic base. However,
platinum or other catalysts would be expensive and the costs, prohibitive. Hence, commercially may not be viable.
With the find of crude at newer geographies and regions, new Oil refineries are being sited close to Ports to optimize logistics. To
support, the major refineries, a number of downstream supporting units, like Distillation units have sprung up in the interiors of
the country. But Napthenic base has been, largely, elusive.
In Sweden and parts of US (Louisiana grade rather than Pennsylvania grade) we get Napthenic Base Stocks. And these may be
further hydrotreated which improves the appearance and colour to bright and clear and water-white.

Typically, Naphthenic grades, have carbon content (Cn ) of approx. 45 (as against Cn in the 30‟s for Paraffinic Base Oils).
Further, the Aniline Point of Napthenic Base would be higher, typically above 63 but lesser than 84.
 Aniline Point – Napthenic Base Oils – 63 to 84
 Aniline Point – Paraffinic Base Oils – above 84
 Aniline Point – Aromatic Base Oils – below 63
Aniline Point follows an interesting pattern. When we study Flash Point of dearomatised solvents, we found a distinct
relationship between Flash Point and Aniline Point. The lower Flash Point grades (D120= 82) have borderline Aniline values (in
the 80‟s). Aniline value increases with increasing Flash Point and (D140 = 88) crosses the benchmark of 84, making it Paraffinic.
Another distinct feature, of Naphthenic Grades is the carbon atom spread.
 Paraffinic Base Oils- Cp 60‟s Cn 30‟s Ca <10
 Napthenic BaseOils- Cp 50‟s Cn 35to45 Ca <10
 Aromatic Base Oils - Cp 50to 55 Cn 30to35 Ca > 10
As stated in (https://www.machinerylubrication.com/Read/30730/base-oil- formulations,) eventhough Naphthenicoil is
mineral-based,itisconsidered a GroupV,oilbecause itdoes not satisfytheAPI‟squalifications for Group I, II and III.
The unique characteristics of naphthenic mineral oils have often made them good lubricants for locomotive engine oils,
refrigerant oils, compressor oils, transformer oils and process oils.
The bottoms of Crude Oil distillation is usually Bitumen and asphalt. Around this, we get a “Cut” known as Extract. These have
high aromatics Ca above 10. These are Aromatic base and known for their solvency and are widely used in the manufacture of
Rubber and Ink Oils. In Natural Rubber (NR) the aromatic constituent assist in speedy solvency for the various Rubber chemicals
(Zinc, Sulphur etc..) used. In this instance, the oil acts as a Plasticizer, that assists in the milling of Natural Rubber (NR) and also in
Printing Inks. These can be classified as Group I base Oils.
# 4
What are the categories of Base oils and how Groups I, II, III, IV, V are named and defined?
The American Petroleum Institute (API) has categorized, Base Oils as Group I, II,III, IV and V, by their properties. Each of the
subsequent Groups undergo additional processing or refining, consequently their basic properties too, undergo changes or
improvements.
As a result, each subsequent group is a better product in terms of key lubrication properties likes lesser saturates, lower
Sulphur, oxidation stability and higher Viscosity Index, Pour Point etc… More details along with process to achieve the relevant
API Grouping ( I, II, III, IV, V) is tabulated below:
Further, as additional refining takes place the category changes from Mineral Oil based to synthetic types. Groups I, II and III are

deemed Mineral oil based. Group IV and V are deemed Synthetic grades. These improvements and its limits are detailed
further and are posted below clearly identifying the Mineral oil from the synthetics. The severely hydrocracked or Group III, is a
mineral oil by API definition.
A recent study on the use of base oils show that,
 Present-day Group IIbaseoilsare the mostcommonly used baseoils, making upto 47 percent of the capacity.
 This is comparedto21percent for bothGroupIIandIIIbaseoils justa decade ago.
 Currently, Group III accounts for less than 1 percent of the capacity in plants.
 GroupI baseoils previously madeup56percent of the capacity,compared to 28 percent of the capacity today.
#5
What is the nomenclature used in Base Oils to categorize different processes or grades?
Base oils have always been classified by their viscosities. Use of SUS units at 100°F ( 40°C ) was in vogue earlier. Nowadays, the
metric system, with units, centi Stokes (cSt) units are in use. Typical grades are as follows:
Group I Base Oils: Manufacture of these grades used standard fractional distillation process and use furfural as Solvent. As
these are also known as Solvent Neutral (SN), hence the use of SN was tagged as prefix. For Aramco Base Oils the names would
read, Dura Series for Group I and Prima Series for Group II
Group I and Group II - Approximate conversion SUS to cSt Group I & II Base Oils
Group I - SUS at 100°F ( = 4°0C) Group II – SUS at 100°F (= 40°C) cSt at 40 C ( = 100°F) Group I & II
Aramco Dura SN40 Aramco Prima 40N 4.5
Aramco Dura SN50 Aramco Prima 50N 7
Group II Base Oils: - these grades are Hydrotreated after fractional distillation. To differentiate them from Group I Base oils,
which are available in the similar viscosities, the nomenclature used for Group II, has a suffix of N (not prefix.) Thus grades
would read as 40N, 50N, 60N, 100N,110N, 230N, 500N.

Group III Base Oils: These grades undergo additional refining under a process called Hydrocracked and their nomenclature
carries their brand/product names with suffix of their viscosities in cSt at 100C. Typical names for Adnoc Group III oils would be
ADbase 2, ADbase 3, ADbase4, ADbase 6, ADbase 8.
Group III Oils – Viscosity at 100°C in cSt (and at 40°C for reference)
Brand name for Adnoc Group III Viscosity at 100°C in cSt Viscosity at 40°C
ADbase 2 2 7.6
ADbase 3 3 14
ADbase 4 4 20
ADbase 6 6 34
ADbase 8 8 49
#6
What are API Base Oil Groups?
In the early 1990s, the American Petroleum Institute implemented a system for describing various base oil types. The result
was the development and introduction of base oil group numbers. Group I base oils are the traditional older base oils created
by a solvent refining technology used to remove the weaker chemical structures or bad actors (ring structures, structures
with double bonds) from the crude oil. Solvent refining was the primary technology used in refineries built between 1940 and
1980.
Group I base oils typically range from amber to golden brown in color due to the sulphur, nitrogen and ring structures
remaining in the oil. They typically have a viscosity index (VI) from 90 to 105. The base oils on the high end of the scale are
often referred to as having a high viscosity index (HVI).This relates to how much the viscosity changes with temperature, i.e.,
how much it thins out at higher temperatures and thickens at low temperatures.
Group I base oils are the most common type used for industrial oils, although increasingly more Group II base oils are being
used.
Group II base oils are created by using a hydro-treating process to replace the traditional solvent-refining process. Hydrogen gas
is used to remove undesirable components from the crude oil. This results in a clear and colorless base oil with very few sulphur,
nitrogen or ring structures.
The VI is typically above 100. In recent years, the price has become very similar to Group I base oils. Group II base oils are
still considered to be mineral oils. They are commonly used in automotive engine oil formulations.
Group II “Plus” is a term used for Group II base oils that have a slightly higher VI of approximately 115, although this
may not be an officially recognized term by the API.
Group III base oils are again created by using a hydrogen gas process to clean up the crude oil, but this time the process is
more severe and is operated at higher temperatures and pressures than used for Group II base oils. The resulting base oil is
clear and colorless but also has a VI above120. In addition, it is more resistant to oxidation than Group I oils.
The cost of Group III base oils is higher than Group I and II. Group III base oils are considered mineral oils by many technical
people because they are derived directly from the refining of crude oil. However, they are considered synthetic base oils by
other people for marketing purposes due to the belief that the harsher hydrogen process has created new chemical oil
structures that were not present before the process. It has synthesized (created)these new hydrocarbon structures.
Group I, II and III base oils basically reflect the evolution in refining technology over the past 70 or 80 years.
Group IV base oils are Polyalphaolefins (PAO) synthetic base oils that have existed for more than 50 years. They are pure
chemicals created in a chemical plant as opposed to being created by distillation and refining of crude oil (as the previous groups
were).PAOs fall into the category of synthetic hydrocarbons (SHCs). They have a VI of greater than 120 and are significantly more
expensive than Group III base oils due to the high degree of processing needed to manufacture them.

Group V base oils comprise all base oils not included in Groups I, II, III or IV. Therefore, naphthenic base oils, various
synthetic esters, Polyalkyleneglycols (PAGs), Phosphate esters and others fall into this group
Typical costs of the various types of Base Oils
#7
Will the Paraffinic Type Base Oil fall under a particular Group I, II & III. What about Napthenic base oils?
A Group I oil is produced by the basic process, fractional distillation under vacuum and carry SN as a prefix in the
nomenclature. SN60, SN70 etc.
While a Group II is further hydro treated (treated with hydrogen) and carry N in the nomenclature, as in 60N, 70N, etc. this
results in removal of saturates, waxes and improved Viscosity Index.
When Group II Base oil is treated further and hydro treated and thereafter hydrocracked it becomes classified as a
Group III Oil.
The source or region of the oil drilling, decides if it Paraffinic or Napthenic. Most oils are Paraffinic in nature. However
some pockets like in Scandinavia, USA are source of Naphthenic Base Oils.
As stated in https://www.machinerylubrication.com/Read/30730/base-oil- formulations,eventhoughNaphthenicoil is
mineral-based,it is considereda GroupVoilbecause it does notsatisfy theAPI‟squalificationsforGroupI, II andIII.
# 8
Is Group III base oil available only in 4 different viscosities?
During the advanced distillation process, hydro-treatment, de-waxing followed by synthesis, most of the wax and saturates are
removed. The high molecular weight components are removed. The synthesis ensures that they are tailored to have controlled
molecular structure. Moreover the severe hydro-processing removes the rings, as well. All these processing and the removal of
high molecular weight components in oils also, brings down the viscosity.
Finally, the end use is mostly for Engine Oils. Over the past decade Engine Oils are offered at lower viscometrics (0W or 5W is
common) as it has been established that fuel economy improves, while oil consumption and energy loss reduces with lower ( 0W
or 5W) viscometrics.
It is also necessary to signalize difference with Group I and Group II grades available in the market. Thus, it is marketed as
Group III -2, 3, 4, 6, 8 meaning, of viscosity 2, 3, 5, 6, 8 cSt at 100°C.

Typical names for Adnoc Group III oils would be ADbase 2, ADbase 3, ADbase 4, ADbase 6 & ADbase 8.
Group III Oils – Viscosity at 100°C in cSt (and at 40°C for reference)
Brand name for Adnoc Group III Viscosity at 100°C in cSt Viscosity at 40°C
ADbase 2 2 7.6
ADbase 3 3 14
ADbase 4 4 20
ADbase 6 6 34
ADbase 8 8 49
#9
Most of the base oil has flash points of 180 or more. MWO have lower flash points specially in Rust preventives and Neat
Cutting Oil?
When we take up vacuum and fractional distillation, different contents or components in the oil get separated at its Boiling
Point, which is unique. At this point it changes phase from Liquid to a gas phase, thereafter it is cooled and this process known as
distillation. Some components boil off, first and could be at temperatures below ambient of 35C. Products that boil off at low
temperature are called Solvents. Typically solvents are volatile and have low flash points and also low viscosities. (Flash below
100C and Viscosities below 7 cSt at 40C). Many of these products have good calorific value and widely used as fuels – Gasoline,
diesel, Kerosene, Aviation fuel and closer to the bottoms called Bunker Fuels etc.. Because of the volatile nature and low
viscosity they do not leave a film and not suitable as a lubricant.
The Lube fraction comes next. For a Lubricant to function it must form a film on the surface that is generated when there is
“sufficient” viscosity in the fluid. Most of the Lubricants have viscosity of over 32 cSt at 40 like in Hydraulic Oils.Whereever,
there areveryhighspeedoperationslikespindles in knitting factory, and lower viscosity oils 7 to 10 cSt is preferred.
To summarize,theboilingpointofeachcomponentisdirectlyproportional to itsviscosityandflash point. Taking 32 cSt as
a reference the flash point is about 200C+ and as viscosity increases, the flash point too, increases proportionally. And as base oil
may be deemed to be Newtonian fluids, follow a linear path, with (Flash Point) increasing proportionally to increase in viscosity.
MWO have different applications, while some operations like Milling and cutting have substantial metal removal, an oily MW
Fluid is used. Many high speed or final cutting operations like Grinding, Honing are finishing operations and metal removal is low
and it is critical that heat generated is dissipated. This can be achieved by a Coolant or a low viscosity oil.
As coolants are an emulsion, water based products can lead to rust and corrosion if residence time is increased while storing
or packing or when the pH of the fluid falls below 9. To improve finish in MW operations a low-viscosity oil is used. As flash
Point and viscosity are directly proportional many Grinding and Honing oils have low Flash Point, but generally above 120C is
considered as safe working.
Rust Preventives are paints with a shorter life. They have an oil or wax (polymer for Paints) content and a solvent or volatile
component as the carrier for the oil, wax, polymer, coating. When the volatile component Solvent, Mineral Turpentine
evaporates, it leaves a film or coating behind, that protects from rust.
#10
In general what base oils are used in RPO and Neat Cutting Oil?
All Rust Preventives have a solvent component to which a film forming/coating component is added. The solvent acts as the
carrier for the rust protection coating/film, which consists of waxes, polymers, anti corrosion additives etc..The use of
solvents or volatile component, bring down the flash point of the RPO fluid.
Many high speed MW operations ( grinding) or finishing (honing, lapping) operations require dissipation of heat to prevent
burrs, heat spots on the material machined. This can be reduced with use of low viscosity oils. As the viscosity of oil is
proportional to flash point, use of low viscosity oils bring down the Flash Point.
For Metal Working (MW) Paraffinic base oils have been used for the past many years, recent studies show that Napthenic
base Oil provide good stability for some MW operations and selected emulsified products.

# 11
What is a Synthetic oil?
Sometimes when we think of synthetic, it tends to be in direct opposition to natural: synthetic fibers versus natural fibers
(polyester vs cotton), synthetic or artificial dyes versus their natural counterparts (Yellow No. 5 versus turmeric), etc. But with
motor oil, the synthetic versus conventional motor oil debate is quite different: synthetic lubricants are often viewed as
superior to mineral oils. Is this true? If so, what's better about them?
Before we begin to answer that, we must consider what synthetic lubricants actually are. When it comes to motor oil, synthetic
can be a bit of a misnomer. This is because today, not all synthetics are actually synthetics.
But here's the thing, not all synthetics are fully synthetic. In the United States, there are no federal guidelines for using the word
synthetic in the distribution and sale of motor oils. So, when a lubricant is called synthetic, it might not actually be synthetic at
all, but rather a highly refined mineral oil.
In 1999, Mobil filed a complaint with the Better Business Bureau's National Advertising Division (NAD) against Castrol Syntec
motor oil. At the time of the litigation, Mobil 1 was made using a PAO base stock synthesized from ethylene while Castrol
Castrol Syntec, on the other hand, was comprised of highly refined crude oil. Mobil's complaint centered around Castrol
marketing their product as synthetic, despite the fact that it was made from petroleum.
Ultimately, the NAD ruled that both Mobil 1 and Castrol Syntec had near identical performance characteristics, despite their
differing base stocks. Further, they said Syntec was technically synthesized from crude oil because its molecular arrangement
was unnatural a byproduct of an intended chemical reaction.
The NAD's ruling has changed the meaning of synthetics as they apply to motor oil, and has led to the differentiation of true
synthetic oils those that are made with chemically synthesized base stocks, such as PAO, Polyalkylene glycol, and/or esters. This
rather broad definition of synthetic oil also imposes the challenge of determining quality based on the term synthetic alone.
(Source: Extracted from https://petroleumservicecompany.com/blog/understanding-synthetic-oils/)
For readers/members wishing to know more, web-links to Base Oils and Solvents refining and its processes and API
Groups are provided below:
1. https://www.machinerylubrication.com/Read/29113/base-oil-groups
2. https://www.stle.org/Images/pdf/LubeCafe/LubeFundamentals/BaseOils/Understandin g_Basestocks/Understanding_Basestocks2.pdf
3. https://petroleumservicecompany.com/blog/understanding-synthetic-oils/)
4. https://club.mobilindustrial.com/lube_talk/b/product_and_application_expertise/posts/engine-oil-fundamentals-part-1-back-to-basics-
with-base-oils-in-engines

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