Note: Descriptions are shown in the official language in which they were submitted.
CA 02319968 2000-09-19
Lubricating Oil Compositions
This invention relates to multigrade lubricating oil compositions that, in
particular, give enhanced performance in diesel engine ring-sticking tests.
Lubricating oil compositions (or lubricants) for the crankcase of internal
combustion engines are well-known and it is also well-known for them to
contain
additives (or additive components) to enhance their properties and
performance.
Increasingly, the demands of original equipment manufacturers (OEM's) to meet
performance criteria dictate the properties of lubricants. One such
performance criterion
concerns the sticking of piston rings during operation of a compression-
ignited (diesel)
internal combustion engine. This is usually referred to briefly as "ring-
sticking"; it may
be measured by the VWTDi test (CEC L-78-T-97).
Other performance criteria of interest include the volatility of the
lubricant, the
fuel economy performance of the lubricant, and the chlorine content of the
lubricant.
The various criteria clearly constrain formulators of lubricants in terms of
additive
components and amounts, and of basestocks, that may be used.
.It has now been surprisingly found, according to this invention, that use of
low
concentrations of molybdenum, present as an organo molybdenum compound, can
give
rise to lubricants meeting demanding "ring-sticking" test requirements,
whilst, at the same
time, meeting other criteria.
A number of references describe the use of oil-soluble molybdenum in
lubricants.
See, for example, US-A-4,164,473; -4,176,073; -4,176,074; -4,192,757; -
4,248,720; -
4,201,683; -4,289,635; and -4,479,883. But none describes use for ameliorating
"ring-
sticking".
In a first aspect, the invention is an SAE OW-30 or 5W-30 or 5W-20 multigrade
lubricating oil composition having a Noack volatility of less than 15, such as
less than 13,
preferably less than 11, preferably no lower than 4 or 5, % mass loss
according to CEC L-
40-A-93; and, optionally, an M-111 fuel economy of equal to or greater than
1.5, such as
2.5%, according to CEC L-54-T-96, said composition comprising, or being made
by
admixing, a major amount of
CA 02319968 2000-09-19
(A) a basestock of lubricating viscosity that contains fronl 0 to less than
10, preferably
from 0 to less than 5, mass % of a Group I basestock or a Group II basestock
or a
mixture of Group I and Group II basestocks, other than basestocks that arise
from
provision of additive components in the composition; and minor amounts of
additive components comprising
(B) one or more molybdenum-containin(Y additives in an amount providing not
greater
than 1000, advantaQeously not greater than 500, such as not greater than 350
or
300 or 250, such as no lower than 50, ppm by mass of elemental molybdenum in
the composition;
(C) one or more calcium detergent additives comprising a calcium salt of an
organic
acid as a surfactant, in an amount or amounts providing 10 or greater, such as
12
or greater, such as up to 30 or 35, m moles of surfactant per kilogram of the
composition;
(D) one or more other lubricant additives selected from ashless dispersants,
metal
detergents, anti-oxidants, anti-wear agents, and friction modifiers, provided
they
are different from additives (B) and (C) above; and
(E) one or more viscosity modifiers,
the additive components providing less than 100, such as less than 50, but
such as no
lower than 5 or 10, ppm by mass of chlorine to the composition.
In a second aspect, the invention is a method of lubricating a compression-
ignited
internal combustion engine comprising operating the engine and lubricating the
engine
with a lubricating oil composition according to the first aspect of the
invention.
In a third aspect, the invention is a method of reducing the ring-sticking
tendencies of a compression-ignited internal combustion engine comprising
adding to the
engine a lubricating oil composition according to the first aspect of the
invention.
In a fourth aspect, the invention is a combination comprising the crankcase of
a
compression-ignited engine and a lubricating oil composition according to the
first aspect
of the invention for lubricating the crankcase.
In this specification:
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CA 02319968 2000-09-19
"comprising" or any cognate word is taken to specify the presence of stated
features, integers, steps or components, but does not preclude the presence or
addition of
one or ntore other features, integers, steps, components or groups thereof;
"major amount" means in excess of 50 mass % of the composition;
"minor amount" means less than 50 mass % of the composition, both in respect
of
the stated additive and in respect of the total mass % of all of the additives
present in the
composition, reckoned as active ingredient of the additive or additives;
"oil-soluble" or "dispersible" used herein do not necessarily indicate that
the
compounds or additives are soluble, dissolvable, miscible, or capable of being
suspended
in the oil in all proportions. These do mean, however, that they are, for
instance, soluble
or stably dispersible in oil to an extent sufficient to exert their intended
effect in the
environment in which the oil is employed. Moreover, the additional
incorporation of
other additives may also permit incorporation of higher levels of a particular
additive, if
desired.
The invention also provides the product obtained or obtainable as a result of
any
reaction between the various additive components of the composition or
concentrates,
essential as well as customary and optimal, under the conditions of
formulation, storage
or use:
The features of the invention will now be discussed in more detail as follows:
Multigrade lubricants
Multigrade lubricants perform over wide temperature ranges. Typically, they
are
identified by descriptors such as SAE IOW-30 or SAE 5W-30. The first number in
the
multigrade descriptor is associated with a safe cranking temperature (e.g., -
20 C)
viscosity requirement for that multigrade oil as measured by a cold cranking
simulator
(CCS) under high shear rates (ASTM D5293). In general, lubricants that have
low CCS
viscosities allow the engine to crank more easily at lower temperatures and
thus improve
the ability of the engine to start at those ambient temperatures.
Multiviscosity -grade oils, commonly referred to as "multigrades" are designed
to operate
over wide temperature ranges and are identified by descriptors such as SAE lOW-
30 or
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SAE 5 W-30,. Their properties are defined in the Society of Automotive
Engineers
document SAE J300. This publication defines multigrades in terms of two
criteria:
Maximum low temperature cranking and pumping viscosities and
Maximum and minimum kinematic viscosities at 100 C and a minimum hiah-shear
viscosity at 150 C and 10gs"'.
Low temperature properties define which "W" grade shall be assigned to a
lubricant and
high temperature properties define the "non W" part of the designation.
SAE J300 defines a series of W grades with SAE OW representing the
requirements for
operation at lowest temperatures. SAE 5W, lOW, 15W, 20W and 25W are also
defined,
these grades are suitable for progressively higher minimum temperature of
operation.
Non-W grades are also assigned a numerical designation, these define a scale
of
increasing high temperature viscosity. This scale starts with SAE 20 and goes
through
SAE 30, 40 and 50 to the most viscous grade, SAE 60.
This system of viscometric classification of automotive crankcase lubricants
finds
universal application with the vehicle and lubricant manufacturing industries.
Noack Volatility
Oil volatility has been associated in the technical literature with both oil
consumption and exhaust emissions, both of which are undesirable. One method
used to
measure volatility of a lubricant is the Noack method. Two standardized Noack
methods
are JPI Method 5S-41-93 and CEC L-40-A-93. Those methods measure the percent
mass
lost after a sample has been held at a temperature of 250 C for 60 minutes
whilst air is
passed through. For the purposes of this invention, all Noack volatility
measurements are
made using instruments that have been calibrated with a reference fluid.
4
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Fuel Economy
M-1 11 fuel economy is as measured in accordance with CEC-L-54-T-96.
(A) Basestock
The basestock (sometimes referred to as "base oil") is an oil of lubricating
viscosity and is the primary liquid constituent of a lubricant into which
additives and
possibly other oils are blended to produce the final lubricant.
Basestocks may be categorised in Groups I to V according to the API Engine Oil
Licensing and Certification System (EOLCS) API 1509 definitions, which
definitions are
used to define the basestocks of this invention. Thus:-
a) Group I basestocks contain less than 90 per cent saturates and/or greater
than 0.03
per cent sulfur and have a viscosity index greater than or equal to 80 and
less than 120
using the test methods specified in Table E-1.
b) Group II basestocks contain greater than or equal to 90 per cent saturates
and less
than or equal to 0.03 per cent sulfur and have a viscosity index greater than
or equal to 80
and less than 120 using the test methods specified in Table E-1.
c) Group III basestocks contain greater than or equal to 90 per cent saturates
and less
than or equal to 0.03 per cent sulfur and have a viscosity index greater than
or equal to
120 using the test methods specified in Table E-1.
d) Group IV basestocks are polyalphaolefins (PAO).
e) Group V basestocks include all other basestocks not included in Group I,
II, III, or
IV.
(B) Molybdenum-containing additives
The molybdenum may, for example, be used in oxidation states IV, and V, such
as
known in the art. The molybdenum may be present as a cation, but this is not
essential.
Thus, for example, molybdenum-containing complexes may be used.
Examples of molybdenum compounds that may be used include the molybdenum
salts of inorganic and organic acids (see, for example, U.S. Patent No. 4 705
641),
particularly molybdenum salts of monocarboxylic acids having from 1 to 50,
preferably 8
to 18, carbon atoms, for example, molybdenum octanoate (preferably 2-
ethylhexanoate),
CA 02319968 2000-09-19
naphthenate or stearate; the reaction product of molybdenum trioxide, molybdic
acid or an alkali
metal salt thereof (or the reaction product of such a molybdenum compound and
a reducing
agent) and a secondary amine having hydrocarbon groups having 6 to 24 carbon
atoms (see EP-
A-205 165); overbased molybdenum-containing complexes as disclosed in EP-A-404
650,
molybdenum dithiocarbamtes and, less preferred because of their phosphorus
content,
molybdenum dithiophosphates; oil-soluble molybdenum compounds as disclosed in
U.S. Patent
Nos 4,995,996 and 4,966,719, particularly the molybdenum xanthates and
thioxanthates
described in those specifications; and oil-soluble molybdenum and sulfur-
containing complexes.
Specific examples of molybdenum- and sulfur-containing complexes are those
prepared by
reacting an acidic molybdenum compound with a basic nitrogen-containing
substance and then
with a sulfur source (see, for example, GB-A-2 097 422), and those prepared by
reacting a
triglyceride with a basic nitrogen compound to form a reaction product,
reacting the reaction
product with an acidic molybdenum compound to form an intermediate reaction
product, and
reacting the intermediate reaction product with a sulfur-containing compound
(see, for example,
GB-A-2 220 954). Other examples of molybdenum compounds are described in
International
Patent Application No. WO 98/26030, published June 18, 1998 and comprise a
trinuclear
molybdenum core, optionally containing non-metallic atoms consisting wholly or
partly of
sulfur, and bonded thereto ligands capable of rendering the compound oil-
soluble or oil-
dispersible. The compounds may be represented by the general formula Mo3SkLp.
wherein
L represents a ligand, for example dithiocarbamate
p is in the range from 1 to 4 and
k is at least 4, especially 4 to 10, preferably 4 to 7.
(C) Calcium detergents
A detergent is an additive that reduces formation of piston deposits, for
example high
temperature varnish and lacquer deposits, in engines; it normally has acid-
neutralising properties
and is capable of keeping finely-divided solids in suspension. Most detergents
are based on metal
"soaps", that is metal surfactants or salts of acidic organic compounds.
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Detergents generally comprise a polar head with a long hydrophobic tail, the
polar
head comprising a metal salt of an acidic organic compound. The salts may
contain a
substantially stoichiometric amount of the metal, in which case they are
usually described
as normal or neutral salts, and would typically have a total base number or
TBN (as may
be measured by ASTM D2896) of from 0 to 80. Large amounts of a metal base can
be
included by reacting an excess of a metal compound, such as an oxide or
hydroxide, with
an acidic gas such as carbon dioxide. The resulting overbased detergent
comprises
neutralised detergent as the outer layer of a metal base (e.g. carbonate)
micelle. Such
overbased detergents may have a TBN of 150 or greater, and typically of from
250 to 450
or more.
The calcium detergents that may be used include oil-soluble neutral and
overbased
sulfonates, phenates, sulfurized phenates, thiophosphonates, salicylates, and
naphthenates. Particularly convenient calcium detergents are neutral and
overbased
calcium sulfonates having a TBN of from 20 to 450 TBN, and neutral and
overbased
calcium phenates and sulfurized phenates having a TBN of from 50 to 450.
Sulfonates may be prepared from sulfonic acids, which are typically obtained
by
the sulfonation of alkyl-substituted aromatic hydrocarbons such as those
obtained from
the fractionation of petroleum or by the alkylation of aromatic hydrocarbons.
Examples
included those obtained by alkylating benzene, toluene, xylene, naphthalene,
diphenyl or
their halogen derivatives such as chlorobenzene, chlorotoluene and
chloronaphthalene.
The alkylation may be carried out in the presence of a catalyst using
alkylating agents
having from 3 to more than 70 carbon atoms. Alkaryl sulfonates usually contain
from 9
to 80 or more, preferably from 16 to 60, carbon atoms per alkyl-substituted
aromatic
moiety.
Oil-soluble sulfonates or alkaryl sulfonic acids may be neutralised with
oxides,
hydroxides, alkoxides, carbonates, carboxylate, sulfides, hydrosulfides,
nitrates, borates
and ethers of the calcium. The amount of calcium compound is chosen having
regard to
the desired TBN of the final product but typically ranges from about 100 to
220,
preferably at least 125, mass %.
,
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Calcium salts of phenols and sulfurised phenols are prepared by reaction of
the
phenol with an appropriate calcium compound such as an oxide or hydroxide, and
neutral
or overbased products may be obtained by methods known in the art. Sulfurised
phenols
may be prepared by reacting a phenol with sulfur or a sulfur - containing
compound such
as hydrogen sulfide, sulfur monohalide or sulfur dihalide to form products
which are
generally mixtures of compounds in which two or more phenols are bridoed by
sulfur-
containing bridges.
(D) Other lubricant additives
- ashless dispersants are non-metallic organic materials that form
substantially no
ash on combustion. Their primary function is to hold solid and liquid
contaminants in
suspension and they comprise long-chain hydrocarbons, to confer oil-
solubility, with a
polar head capable of associating with particles to be dispersed. A noteworthy
group is
hydrocarbon-substituted succinimides
- anti-oxidants increase the composition's resistance to oxidation and may
work by
combining with and modifying peroxides to render them harmless by decomposing
peroxides or by rendering an oxidation catalyst inert. They may be classified
as radical
scavengers (eg sterically hindered phenols, secondary aromatic amines, and
organo-
copper salts);hydroperoxide decomposers (eg organo-sulfur and organophosphorus
additives); and multifunctionals. In the practice of the present invention,
the use or
otherwise of certain anti-oxidants may confer certain benefits. For example,
in one
embodiment it may be preferred that the lubricating oil composition is free of
any
secondary aromatic amine anti-oxidants. In another embodiment, it may be
preferred to
employ in the lubricating oil composition a combination of one or more
secondary
aromatic amine anti-oxidants (eg in the range of 0.1 to 0.7, preferably 0.2 to
0.5, mass %
of the composition) and one or more sterically hindered phenol anti-oxidants
(eg in the
range of 0.1 to 2, preferably 0.5 to 1.5 mass % of the composition); such
composition
may for example contain one or more molybdenum-containing additives in an
amount
providing from 50 or 100 to 500 or 700 ppm by mass of elemental molybdenum in
the
composition.
8
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- anti-wear agents reduce friction and excessible wear and are usually based
on
compounds containing sulfur or phosporus or both. Noteworthy are metal
dihydrocarbyl
dithiophosphates such as zinc dialkyl dithiophosphates (ZDDP's). Preferably,
the alkyl
groups are essentially secondary alkyl groups.
- friction modifiers include boundary additives that lower friction
coefficients and
hence improve fuel economy. Examples are esters of polyhydric alcohols such as
glycerol monoesters of higher fatty acids, for example glycerol mono-oleate;
esters of
long chain polycarboxylic acids with diols, for example the butane diol esters
of
dimerized unsaturated fatty acids; oxazoline compounds; and alkoxylated alkyl-
substituted mono-amines, and alkyl ether amines, for example, ethoxylated
tallow amine
and ethoxylated tallow ether amine. Preferably, in the practice of this
invention,
component(s) (D) includes one or more friction modifiers selected from esters
of
polyhydric alcohols and from alkoxylated amines.
(E) Viscosity Modifiers
Viscosity modifiers (or viscosity index improvers) impart high and low
temperature operability to a lubricating.oil. Viscosity modifiers that also
function as
dispersants are also known and may be prepared as described above for ashless
dispersants. In general, these so-called dispersant viscosity modifiers are
functionalized
polymers (e.g. interpolymers of ethylene-propylene post-grafted with an active
monomer
such as maleic anhydride) which are then derivatized with, for example, an
alcohol or
amine.
Suitable compounds for use as viscosity modifiers are generally high molecular
weight hydrocarbon polymers, including polyesters. Oil-soluble viscosity
modifying
polymers generally have weight average molecular weights of from 10,000 to
1,000,000,
preferably 20,000 to 500,000, which may be determined by gel permeation
chromatography or by light scattering.
Representative examples of suitable viscosity modifiers are polyisobutylene,
copolymers of ethylene and propylene and higher alpha-olefins,
polymethacrylates,
polyalkylmethacrylates, methacrylate copolymers, copolymers of an unsaturated
dicarboxylic acid and a vinyl compound, interpolymers of styrene and acrylic
esters, and
9
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partially hydrogenated copolymers of styrene, isoprene, styrene/butadiene, and
isoprene/butadiene, as well as the partially hydrogenated homopolymers of
butadiene and
isoprene and isoprene/divinylbenzene.
Other known additives may be incorporated into the lubricating oil
compositions
of the invention, being different from those defined in the invention. They
may, for
example, include other detergents; rust inhibitors; corrosion inhibitors; pour
point
depressants; anti-foaming agents; and surfactants. They can be combined in
proportions
known in the art.
As is known in the art, some additives can provide a multiplicity of effects;
thus,
for example, a single additive may act both as a dispersant and as an anti-
oxidant.
As stated above, the additives provide less than 50 ppm by mass of chlorine to
the
composition. Thus, to meet this requirement, the use of chlorine-containing
additives (eg
arising from their method of manufacture) must be eliminated or at least
controlled.
CONCENTRATE DEFINITION
In the preparation of lubricating oil compositions, it is common practice to
introduce additive(s) therefor in the form of concentrates of the additive(s)
in a suitable
oleaginous, typically hydrocarbon, carrier fluid, e.g. mineral lubricating
oil, or other
suitable solvent. Oils of lubricating viscosity such as described herein, as
well as
aliphatic, naphthenic, and aromatic hydrocarbons, are examples of suitable
carrier fluids
for concentrates.
Concentrates constitute a convenient means of handling additives before their
use,
as well as facilitating solution or dispersion of additive in lubricating oil
compositions.
When preparing a lubricating oil composition that contains more than one type
of
additive, each additive may be incorporated separately - each in the form of a
concentrate.
In many instances, however, it is convenient to provide a so-called additive
"package"
(also referred to as an "adpack") comprising two or more additives in a single
concentrate.
A concentrate may contain I to 90, such as 10 to 80, preferably 20 to 80, more
preferably 20 to 70, mass % active ingredient of the additive or additives.
CA 02319968 2000-09-19
MAKING COMPOSITIONS
Lubricating oil compositions may be prepared by adding to an oil of
lubricating
viscosity a mixture of an effective minor aniount of at least one additive
and, if necessary,
one or more co-additives such as described hereinafter. This preparation may
be
accomplished by adding the additive directly to the oil or by adding it in the
form of a
concentrate thereof to disperse or dissolve the additive. Additives may be
added to the oil
by any method known to those skilled in the art, either prior to,
contemporaneously with,
or subsequent to addition of other additives.
The lubricating oil compositions may be used to lubricate mechanical engine
components, particularly an internal combustion, such as a compression-ignited
engine,
by adding the lubricating oil thereto. Particular examples of compression-
ignited engine
are those developed in recent years where the top ring groove temperature may
exceed
150 C due to increases in specific power output to around 40 kW/litre or
greater. These
engines are more prone to suffer from ring-sticking problems in their
operation.
When concentrates are used to make the lubricating oil compositions, they may
for example be diluted with 3 to 100, e.g. 5 to 40, parts by mass of oil of
lubricating
viscosity per part of the concentrate.
When lubricating oil compositions contain one or more additives, each additive
is
typically blended into the base oil in an amount which enables the additive to
provide its
desired function. Representative effective amounts of such additives, when
used in
crankcase lubricants, are listed below. All the values listed herein are
stated as mass per
cent active ingredient, unless otherwise indicated.
11
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ADDITIVE MASS % MASS %
(Broad) (Preferred)
Ashless Dispersant 0.1 - 20 1-8
Metal detergents 0.1 - 6 0.2 - 4
Corrosion Inhibitor 0-5 0- 1.5
Metal dihydrocarbyl dithiophosphate 0.1 - 6 0.1 - 4
Supplemental anti-oxidant 0-5 0.01 - 1.5
Pour Point Depressant 0.01 - 5 0.01- 1.5
Anti-Foaming Agent 0-5 0.001-0.15
Supplemental Anti-wear Agents 0- 0.5 0- 0.2
Friction Modifier 0-5 0- 1.5
Viscosity Modifier 0.01- 6 0-4
Mineral or Synthetic Base Oil Balance Balance
The final composition may contain from 5 to 25, preferably 5 to 18, typically
10
to 15, mass % of the concentrate, the remainder being oil of lubricating
viscosity.
EXAMPLES
The invention will now be particularly described, by way of example only, as
follows:-
Four additive packages (or "adpacks") were prepared by methods known in the
art
and identified as Packages 1, A, 2 and B. The packages were identical except
that
Packages 1 and 2 contained molybdenum (in the same concentrations) and
Packages A
and B did not, and that Packages I and A contained less dispersant than
Packages 2 and
B, Packages 1 and A having identical dispersant-concentrations, and Packages 2
and B
having identical dispersant-concentrations.
Each package contained the following additives in the same concentrations:
polybutene succinimide dispersant
overbased calcium sulfonate detergent
overbased magnesium sulfonate detergent
neutral calcium sulfonate detergent
neutral calcium phenate
12
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hindered phenol antioxidant
ethoxylated amine friction modifier
glycerol mono-oleate friction modifier
zinc dialkyl dithiophosphate anti-wear agent
silicone anti-foamant
demulsifier
diluent oil
Packages I and 2 contained a trinuclear molybdenum/sulfur thiocarbamate.
Packages 1
and A contained less dispersant than Packages 2 and B.
Each package .vas blended into a Group IV basestock mixture to give an SAE
OW-30 lubricating oil composition (or oil) having the following
characteristics, wherein
each oil is identified by the same reference numeral or letter as the package
from which it
was blended.
OIL
A 2 B
Noack Volatility 10.7 10.6 11 10.6
Cl-content (ppm) 26 26 26 26
Mo-content (ppm) 100 0 100 0
Surfactant content 14.2 14.2 14.2 14.2
(mmoles/Kg)
Dispersant content 2.6 2.6 3.5 3.5
(mass %)
Tests and Results
Samples of each of Oils 1, A, 2 and B were subjected to VWTDi CEC-L-78-T-97
tests.
13
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The results are set out in the table below.
OIL
I A 2 B
merits' 65 46 68 56
ring stick2 0 2.63 0 0.63
(average)
ring stick3 0 5.0 0 2.5
(maximum)
Each test was run to its full duration, ie not terminated prematurely
I. ACEA B4limit is > 65
2. ACEA B4 limit is < 0.7
3. ACEA B4 limit is < 2.5
The results clearly demonstrate the beneficial effect of low levels of
molybdenum
in the tests. Thus, their incorporation converts oils from those that fail the
test to those
that comfortably pass, which is observed at both high and low dispersant
levels.
In a further example of the invention, an SAE 5W-30 lubricating oil
composition
(Oil 3) was prepared that contained a trinuclear molybdenum/sulfur
thiocarbamate
additive providing 300 ppm by mass of elemental molybdenum, a diphenyl-amine
anti-
oxidant (0.35 mass %), and a hindered phenol antioxidant (1.1 mass %). Oil 3
possessed
other properties falling within those of the compositions of the first aspect
of the
invention.
Oil 3 was tested in the API Seq III test, but carried out for twice the
stipulated
length of time (128 hours as opposed to 64 hours). The stipulated test is
concerned with
piston cleanliness, cam and lifter wear, and viscosity growth in the oil.
Doubling the
duration of the tests increases its severity: under these conditions, the
viscosity growth
usually becomes the limiting factor and hence control of oil viscosity by use
of additives
becomes critical.
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The results obtained were as follows:
Hours Viscosity
Increase %
0 0
8 5
16 8
24 11
32 13
40 15
48 17
56 19
64 21
72 22
80 23
88 24
96 26
104 27
112 28
120 31
128 34
Under the ACEA AI-98 (ASTM D 5533) specification for the Seq III E test, the
oil viscosity increase at 40 C must be <_ 100%. The above results therefore
demonstrate
that the oil tested (Oil 3), employing a mixture of two different anti-
oxidants, showed
exceptional performance in the severe version of that test carried out as
described above.
