ILMA Compoundings September 2018 - 31

byproduct streams, and those were collected as well. Today,
the average crude oil delivers gasoline, diesel fuel, kerosene,
natural gas liquids and liquid refinery gases, petrochemical
feedstocks, petroleum coke and heavy fuel oil, among others. Gasoline takes the largest share of this by far, according
to the U.S. Energy Information Administration, at about
20 gallons (gal.) of motor gasoline and 11 gal. of ultra-low
sulfur distillate fuel oil per 42-gal. barrel of crude oil.
The American Petroleum Institute (API) developed a
classification system for base oils based on their physical and
chemical properties (base oil groups) when the API 1509
document on the Engine Oil Licensing and Certification
System (EOLCS) was introduced in the early 1990s. This
system has been used in many contexts; the table below
contains the official description of the groups.
Groups I through III are refined and processed in different ways, Group IV includes polyalphaolefins and Group V
is a catch-all.
Group I base oils were the first to be developed. Prior to
the 1920s, base oils were simply what was left after all of
the fuel cuts were removed. The only processing was acid
treatment and clay contacting to remove insoluble and
polar materials.
Solvent refining was developed to capture wax and aromatics and improve the quality of the base oils. To this day,
wax removed by solvent dewaxing is a valuable commodity.
The aromatic materials, which are solvent extracted, are
excellent process oils but are highly toxic and carcinogenic.
Typically, these base stocks require more additive treatment
to produce acceptable motor oils.
Group I base oils have some unique properties, primarily
improved solubility characteristics and range of viscosities
available. The downside is that the presence of aromatics and
lower saturate levels results in the increased need for additive
treatment.
Group II base oils first came into the marketplace in
the 1970s. The process involved hydrotreating to convert
aromatics into paraffinic and naphthenic components. The
hydrotreating process cracked the molecules, creating lower
viscosity fractions. In addition, solvent extraction was no

longer needed. The earliest Group II plants dewaxed using
solvent, so wax was still available. Later, catalytic dewaxing
was developed. This process selectively broke large saturated
molecules into pieces which were about the same molecular
range as the base stock. This process added to the yield but
sacrificed the separate wax production. The primary advantages for Group II included increased yields, more stable
base oils and improved additive response. The negatives
included a reduced range of viscosities available, typically
from about 3cSt to 15cSt at 100 degrees Celsius.
Group III base oils entered the marketplace in the 1980s.
Most are from the Far East and are produced using the
same processes as Group II, only more severe. The result

By the end of the 1860s, there were
58 refineries in Pittsburgh alone.

Group

Viscosity Index

Sulfur, wt.%

Saturates, %

Description

≥ 80 < 120

> 0.03

< 90

Classic solvent-refined base oil

≥ 90 < 120

≤ 0.03

≥ 90

Hydroprocessed base oil

III

≥ 120

≤ 0.03

≥ 90

Severely hydroprocessed base oil

Polyalphaolefins

Everything else

Source: API 1509 Engine Oil Licensing and Certification System, 11th Edition

ILMA Compoundings September 2018

Table of Contents for the Digital Edition of ILMA Compoundings September 2018