Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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001 -1-
002IMPROVING FUEL ECONOMY IN INTERNAL COMBUSTION ENGINES
004FIELD OF THE INVENTION
005This invention relates to a method for improving the
006 fuel economy of an internal combustion engine and to a lubri-
007 cating oil useful in such method.
008 BACKGROUND OF THE INVENTION
_ _ _
009 With the crisis associated with diminishing amounts
010 of fossil fuel and the rapidly increasing prices for this fuel,
011 there has been a great deal of interest in improving fuel
012 economy, that is, the number of miles obtained in a given
013 vehicle per unit of fuel.
014 Pentaerythritol monooleate is an additive which has
015 been widely used especially in the industrial oil area and at
016 low concentrations; that is, less than about one half of 1% in
017 industrial oil or at high concentrations, for example, 5 to
018 10%. U.S. 3,970,570 teaches the combination of tricresyl
019 phosphate and pentaerythritol monooleate at 0.25 to 2 percent.
020 Pentaerythritol monooleate is known to be an oiliness
021 agent, however, since piston and ring lubrication is predom-
022 inantly hydrodynamic, gains in fuel economy through the use of
023 additives in the lubricating oil which reduce the coefficient
024 of friction in mixed lubrication will probably be small and
025 difficult to assess.
026 SUMMARY OF THE INVENTION
027 According to the present invention, a lubricating oil
028 containing pentaerythritol monooleate is taught for use in the
029 crankcase of internal combustion engines. This new oil gives
030 better fuel economy compared to the same oil without the
031 additive.
032 DETAILED DESCRIPTION OF THE INVENTION
033 Adding from 0.25 to 2 weight percent and preferably
034 from 0.4 to 1.25 weight percent, of pentaerythritol monooleate
035 to a crankcase lubricating oil as defined below significantly
036 improves the fuel economy of the internal combustion engine.
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001 -2-
002 Pentaerythritol monooleate as it is commercially
003 available is usually a mixture of mono-, di-, tri- and tetra-
004 oleates of pentaerythritol. Some oleic acid may also be
005 present. As used herein the term pentaerythritol monooleate is
006 intended to include both pure pentaerythritol monooleate and
007 mixtures of pentaerythritol mono-, di-, tri- and tetraoleate.
008 The crankcase lubricants for use with this invention
009 are those which contain an alkali or alkaline earth metal
010 sulfonate or phenate or combinations thereof, a zinc dialkyl
011 dithiophosphate and an alkenyl succinimide. The amount of
012 pentaerythritol monooleate added is that sufficient to reduce
013 fuel consumption of the engine.
014 The pentaerythritol monooleate can be used in mineral
015 oil or in synthetic oils of viscosity suitable for use in the
016 crankcase of an internal combustion engine. Crankcase lubrica-
017 ting oils have a viscosity up to about 85 SUS at 210F.
018 The addition of pentaerythritol monooleate to the
019 lubricating oil as described above results in improved mileage
020 benefits in both compression and spark ignition engines.
021 Crankcase lubricating oils of the present invention
022 usually have a viscosity up to about SAE 40. Sometimes such
023 motor oils are given a classification at both 0 and 10F such
024 as SAE lOW40 or SAE 5W30.
025 Mineral oil for use as the base oil in this invention
026 includes paraffinic, naphthenic and other oils that are
027 ordinarily used in the lubricating oil compositions.
028 Synthetic oils include both hydrocarbon synthetic oil
029 and synthetic esters. Use of synthetic hydrocarbon oils
030 include liquid polymers of alpha olefins having the proper
031 viscosity. Especially useful are the hydrogenated liquid
032 oligomers of C6-12 alpha olefins such as alpha decene trimer.
033 Likewise alkyl benzenes of proper viscosity can be used such as
034 didodecyl benzene.
035 Useful synthetic esters include the esters of both
036 monocarboxylic acid and polycarboxylic acid as well as mono-
037 hydroxy alkanols and polyols. Typical examples are didodecyl
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001 -3-
002 adipate, trimethylol propane, tripelargonate, di(2-ethyl-
003 hexyl)adipate and the like. Complex esters prepared from
004 mixtures of mono and dicarboxylic acids and mono and poly-
005 hydroxy alkanols can also be used.
006 Blends of mineral oil with synthetic oil are also
007 useful. For example, blends of 10-25 weight percent hydro-
008 genated alpha decene trimer with 75-90 weight percent 150 SUS
009 (100F) mineral oil gives an excellent lubricant base.
010 One of the additives of the conventional formulation
011 to which the pentaerythritol monooleate is added in order to
012 give improved mileage benefits is an alkali or alkaline earth
013 metal hydrocarbyl sulfonate. The hydrocarbyl group may be
014 derived from a petroleum fraction, from a synthetically
015 alkylated aromatic fraction or from an aliphatic group such as
016 polyisobutylene. Examples of these are sodium, calcium,
017 magnesium or barium salts of sulfonated petroleum fractions or
018 of polyisobutylene which has been sulfonated. These
019 compositions are well known in the art and include both neutral
020 and overbased sulfonates having base numbers up to about 400 or
021 more. In an ordinary formulation they would be used in an
022 amount to provide from 10 to 100 mmols per kg of alkaline earth
023 metal and preferably from 10 to 60 mmols per kg.
024 The phenate for use in this invention can be any one
025 of those additives conventionally used in lubricating oil for-
026 mulations which are alkali or alkaline earth metal salts of
027 aromatic phenols ordinarily alkylated aromatic phenols wherein
028 the alkylating group has from about 9 to about 300 carbon
029 atoms. The phenol may be mono or dialkylated. Preferable
030 salts are calcium, magnesium or barium salts. The phenates may
031 be sulfurized and may also be neutral or overbased having base
032 numbers up to 400 or more. These phenates are usually used in
033 amounts to provide 10 to 100 mmols per kg alkali or alkaline
034 earth metal and more preferably about 10 to 60 mmols per kg.
035 The zinc dialkyl dithiophosphate contains from 3 to
036 18 carbon atoms in each alkyl group. These compositions are
037 well known in the art. Preferred alkyl groups contain from 6
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to 8 carbon atoms although mixed zinc dialkyl dithiophosphates
may also be used wherein one group contains 3 or 4 carbon atoms
and the other group contains 6 to 8 carbon atoms.
The succinimide present in the formulation is an
alkenyl succinimide prepared by reacting, for example, a poly-
isobutenyl succinic anhydride with a polyethylene polyamine such
as tetraethylene pentaamine. The alkenyl substituent is
preferably a polyisobutene group having a molecular weight from
about 800 to 5,000. Succinimides of this type are described in
United States Patent Nos. 3,172,892 and 3,219,666. The alkenyl
succinimide can be reacted with boric acid or a similar boron-
containing compound to form borated dispersants having utility
in this invention. The borated succinimides are intended to be
included within the scope of the term alkenyl succinimide.
Other additives conventionally used in the art may be
used with the formulation disclosed in this invention. The
formulations used commercially are often multigrade oils.
Multigrade oils are obtained by adding viscosity index improvers
as is well known in the art. Typical viscosity index improvers
include polyalkyl methacrylates or ethylene-propylene copolymers
or styrene diene copolymers. It is also possible to use a
dispersant VI improver.
Tests have been carried out to demonstrate the
improvement in fuel economy obtained by adding pentaerythritol
monooleate. In these tests Ford 302 CID engines were run with
lubricating oils with and without pentaerythritol monooleate.
In the tests the engines were run at either constant
output or constant input. The engines were run on dynamometers
at conditions simulating 55 miles per hour under approximately
road load. In the formulations below, Formulation A refers to
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a lubricating oil composition containing hydrocarbon base oil
and approximately 2.6~ of a borated alkenyl succinimide; 25
mmols per kg of a primary alkyl zinc dithiophosphate; 32 mmols
per kg of an overbased calcium hydrocarbon sulfonate and 15
mmols per kg of an overbased magnesium sulfonate. Formulation
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001 -5-
002 B contains 3.5% of an alkenyl succinimide; a primary alkyl zinc
003 dithiophosphate at 0.14% phosphorus level; 20 mmols per kg of
004 overbased sulfurized calcium phenate, and 30 mmols per kg of an
005 overbased magnesium sulfonate.
006 The results of these tests showing the increase in
007 fuel economy upon addition of the pentaerythritol monooleate
008 are noted below. The comparisons were run side by side.
009% Fuel Economy Improvement
010Constant Output Constant Input
012 Formulation A as a lOW40 1% 3 runs 2.6% 1 run
013 oil vs. Formulation A 1.7% 3 runs
014 as a lOW40 oil contain-
015 ing 1% pentaerythritol
016 monooleate
018 Formulation A as a 2.5% 3 runs
019 lOW oil vs. Formulation A
020 as a lOW oil plus 1%
021 pentaerythritol mono-
022 oleate
024 Formulation B as a lOW30. 1.38% 2 runs
025 oil vs. Formulation B 1.1% 3 runs
026 as a lOW30 oil plus 1%
027 pentaerythritol mono-
028 oleate
030 Formulation C - 3.5% alkenyl succinimide, 50 mmols
031 per kg overbased magnesium sulfonate and 0.14% phosphorus
032 supplied by zinc dialkyl dithiophosphate as a lOW oil
033 containing 1% pentaerythritol monooleate gave in a constant
034 output run 2.3% fuel economy improvement based on 3 sets of
035 data.
036 Formulation D containing 3.5% alkenyl succinimide;
037 50 mmols per kg overbased sulfurized calcium phenate and 0.14%
038 phosphorus supplied by zinc dialkyl dithiophosphate as a lOW
039 oil vs. the same formulation containing also 1% pentaerythritol
040 monooleate in a constant output run gave 1.4% fuel economy
041 improvement based on 3 runs of data.
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001 -6-
002 The relative improvement based on concentration of
003 pentaerythritol monooleate was determined in an engine similar
004 to that used above using constant output conditions with all
005 the other conditions as being described above. The variation
006 of fuel economy improvement of a lOW40 oil with concentration
007 of pentaerythritol monooleate varies as follows:
008 Concentration ofPercent Fuel Economy
009 Pentaerythritol Monooleate Improvement
011 0.25 0.2
012 0.5 0.76
013 1.0 .96
014 1.5 1.02
015 2.0 1.11
016 It can be seen that the effect of pentaerythritol
017 monooleate is most obvious at 1% and that higher concentrations
018 do not give a significant improvement in fuel economy, while
019 areas below 0.25% would not provide sufficient improvement in
020 fuel economy to justify their use when the addition of more
021 pentaerythritol monooleate would provide greater improvement in
022 fuel economy.
023 It is to be noted that the improvements observed vary
024 based on the specific engine operating conditions and can vary
025 from one set of comparisons to the next. The predominant confi-
026 dence level for the data provided herein is at least 80% and
027 oftentimes at least 95% based on statistical methods of
028 analysis.
