2001.M4.4.5
Research on Environment-Friendly Gasoline Engine Oil
of Ultra-Low Viscosity
(GE Oil Ultra-Low Viscosity Group)
Kouichi Kubo, Yoshiharu Baba, Keiichi Moriki, Mitsuhiro Nagakari
1.
Contents of Empirical Research
1.1
R&D Background
Demand for oil in Japan amounts to about 250 million kiloliters per year, and about 40% of this
total is consumed as gasoline, light oil or other motor vehicle fuel. About 20% of total CO2
emissions in Japan are produced by the transport sector, and such emissions are increasing
every year. At the Third Session of the Conference of the Parties to the United Nations
Framework Convention on Climate Change (COP3) held in Kyoto in December 1997,
discussions focused on the reduction of CO2 emissions. It was agreed that the target for
Japan would be a 6% reduction from the CO2 emissions level in 1990. Against this backdrop,
an improvement in fuel consumption of about 20% over the 1995 level by the year 2010 has
become mandatory in the transport sector. Reduction of CO2 emissions from motor vehicles
through still greater efficiency in gasoline and diesel internal combustion engines has become
one of the most crucial issues.
There are numerous methods by which CO2 emissions from motor vehicles can be reduced
(that is, methods by which fuel consumption can be improved), including improvement of engine
combustion efficiency and reduction of vehicle weights. But the method said to be of the
lowest cost to society is one in which engine friction is reduced by filling the vehicle with an
optimised engine oil. Methods involving engine oil are especially convenient and applicable
over a broad range because, unlike methods calling for improved combustion efficiency, etc.,
they do not require changes in engine design, etc.
1.2
R&D Methodology
Under the principle of improved fuel economy in motor vehicles through engine lubricating oil, if
an engine is operated under conditions of high speed and low oil temperature, engine friction
can be reduced by lowering viscosity. At an extremely low viscosity, however, if the engine is
run under conditions of low speed and high oil temperature, it is feared that oil film will get
thinner, metal-to-metal contacts will increase, engine friction force will escalate abnormally, and
heavy wear will be produced. In this situation, there is also a method whereby a adsorbed film
or reaction film can be generated on surfaces by friction modifier additives, thereby preventing
metal-to-metal contact and lowering engine friction. With this method, however, there is
concern about the side effect in which wear protection performance drops sharply due to
competitive adsorption or mutual action between friction modifier and anti-wear additive in the
engine oil. Accordingly, research is required on engine friction and wear when these
technologies have been combined and especially when the lubricant has ultra-low viscosity.
1
Nevertheless, there have been few reports of research on the impact of engine oil of ultra-low
viscosity on engine wear, and to date, no clear methods have been presented regarding
countermeasures. In order to realize engine oil of ultra-low viscosity, the effect of reducing
anti-wear additive will be more significant for the purpose of preventing wear. In general,
however, increasing the effect of anti-wear additive has an adverse effect on emissions
reduction catalysts, and produces environmental pollution when the oil used is treated as waste
oil. Since this method tends to increase the burden placed on environment, it is not considered
a desirable approach.
In the present project, an investigation was made of the impact of engine oil viscosity
characteristics on engine wear and friction. Through clarification of the relationship between
engine oil viscosity and anti-wear additive compositions as opposed to wear or friction, an
engine oil is being developed which offers high oil film forming and retaining capacity, high wear
protection and low engine friction despite being an ultra-low viscosity oil. For this reason, it is
essential to clarify the oil film retention capacity of viscosity index improver or base oil, and to
clarify the engine oil viscosity and engine lubrication domain. Moreover, because the engine
oil does not act to lower wear protection, despite being of ultra-low viscosity, the impact of
engine oil viscosity characteristics on wear protection must be clarified together with the mutual
interactions of anti-wear additive, dispersant, detergent and base oil contained in the engine oil.
Therefore a formulation must be developed which optimises the effect of anti-wear additives.
1.3
Reference Oil versus Test Oil Matrix and Fuel Economy Evaluation Method
In the current research project, in order to make an evaluation and comparative investigation of
fuel economy and wear protection, gasoline engine oil sold on the market and complying with
SAE 5W-30, API SJ, ILSAC GF-2 was set up as the Reference oil (REO) for four years. The
high-temperature, high shear viscosity (HTHSV) of this Reference oil at 150°C and 106 s-1 was
3.10 mPa·s and the phosphorus elemental content in the engine oil was 0.097 mass%.
Furthermore, for the purpose of investigating the impact of friction modifier on fuel economy,
four types of ash-free friction modifier (A, B, C, D) were added to test oil 6 shown in Figure
1.3-1; test oils 6A, 6B, 6C and 6D were then prepared and evaluated for fuel economy.
REO
Figure 1.3-1
Test Oil Matrix
2
In the evaluation of test oil fuel economy, a motored friction tester (Figure 1.3-2) was used.
Here a 1.8L engine having a direct acting valve train system produced in Japan was used;
engine oil temperature ranged from 40°C to 100°C and engine speed was controlled by electric
motor between 600 and 3000 r/min. The low friction characteristic of the test oil was then
evaluated by measuring the friction loss torque thus produced.
Torque
meter
Engine
Intake air:
Temperature.: 26.5±1.0°C
Humidity:
55.0±5%
Figure 1.3-2
Electric
motor
Engine Motored Friction Tester
All the results thus obtained were compared with the friction loss torque value of 5W-30 oil on
the market (REO), which was established as the Reference oil in the current R&D project, and
“friction reduction percentage” was determined. When this value is larger, it shows that the oil
has better high fuel economy. Moreover, it has already been clarified that viscometric
conditions are established when the engine speed is high and engine oil temperature's low, and
that mixed lubricating conditions prevail when the engine speed is low and the oil temperature is
high1).
1.4
Evaluation of Wear Protection of Test Oil
In 1999, the effects of engine oil viscosity and of phosphorus content on engine wear were
clarified. It was also clarified that the manufacture of certain types of lubricant additives for
engine oils can result in the presence of chlorine in the engine oil as an impurity. The
magnitude of chlorine in engine oil can therefore be reduced by carefully selecting each additive.
In 2000, three types of test oil (12 to 14) were prepared, based on the test oil (10) shown in
Figure 1.3-1, by converting dispersant and detergent into additives of low chlorine content
(Table 1.4-1). It was decided to investigate the possibilities of reducing chlorine content by
evaluating anti-wear performance of these test oils.
Table 1.4-1 Test Oil for Investigation of Possibilities for Reducing Chlorine Content
Detergent
Dispersant A
Dispersant B
Supplement:
Sulphonate
Test oil 10
Test oil 13
Salicylate
Test oil 12
Test oil 14
Chlorine content originating from dispersant A is 80 ppm. Chlorine content originating from
sulphonate is 70 ppm. Dispersant B and salicylate were below the detection limit (5 ppm).
In order to investigate the impact of ash-free friction modifier on wear protection, test oils (test
oil 10A, 10B, 14A, 14B) were prepared by adding friction modifiers (A, B) to test oils 10 and 14,
and the anti-wear performance of these oils was evaluated.
3
As in the R&D project in 1999, anti-wear performance of test oils was evaluated using the JASO
valve train wear test method (M328-95). In this test method, among the practical performances
of gasoline engine oil, anti-wear performance of the valve train system was evaluated, and the
test conditions are roughly the same as those of the ASTM Sequence IVA test method, the
international test method. Upwards of 80% of the time, the engine is operated at an engine oil
temperature of 50°C. In this test method, the depth of wear produced at the rocker arm pad
scuffing and at the cam nose is stipulated as the evaluation item. In the present R&D, however,
measurements were taken in consideration of changes in cam configuration before and after
testing. Moreover, all the engine tests were carried out with the oil temperature adjusted to
25°C and relative humidity to 40%, despite the fact that no special intake air temperature or
humidity is stipulated in the M328-95 test method. This is because it is known that the intake
air temperature and humidity have a great impact on test severity 2).
1.5
Evaluation Method for Detergency and High-temperature Oxidation Stability of
Test Oil
The detergency of test oils was evaluated by the JASO detergency test method (M331-91)
using a practical engine. In this test method, the detergency of the engine interior is evaluated
after the engine has been operated. In addition, high-temperature oxidation stability was
evaluated by the JASO high-temperature oxidation stability test method (M333-93), also using a
practical engine. With engine speed at 4800 r/m, engine oil temperature at 149 ±2°C and
duration at 96 hours, this test method is extremely severe for engine oil.
In 1999, impact of ultra-low viscosity on wear protection was investigated, but in 2000, the
detergency and high-temperature oxidation stability of test oil 14 was evaluated for the purpose
of investigating the impact of ultra-low viscosity oil on detergency and on high-temperature
oxidation stability.
1.6
Analysis Method for Lubricant Oil Additive
The quantities of each element in petroleum additives included in the engine oils were
measured. Elemental metallic content was measured by JPI 5S-44-95 (ICP method);
elemental nitrogen content by JIS K 2609; elemental sulfur content by JIS K 2541 and chlorine
content by wave length dispersion fluorescent x-ray spectroscopy (internal standard additive
method).
In order to investigate the mutual interactions of petroleum product additives dissolved in the
lubricant oil, Zeta potential was measured, but each additive was also dissolved in PAO 4
(polyalphaoleffin) solvent and measured. For the dielectric constant at each PAO 4 solvent
temperature, necessary for analysis of Zeta potential measurements, the complex dielectric
constant was measured over the frequency range from 20 Hz to 1 MHz using a dielectric
constant meter.
2.
Results of Empirical Research and Analysis
2.1
Evaluation of Fuel Economy with Test Oil
Firstly, an investigation was made of the impact of engine oil high-temperature, high-shear
(HTHS) viscosity and of low-temperature cranking (CCS) viscosity on fuel economy.
4
Figure 2.1-1 gives the results with engine speed at 3000 r/min and oil temperature at 80°C. By
lowering the HTHS viscosity in increments of 0.5 mPa·s, a low friction effect of about 3% was
measured. The relationship between HTHS viscosity and fuel economy is well known, but in
the present research, it was clarified that the impact is high even when the HTHS viscosity is in
the ultra-low region of 2.1 mPa·s. It was also discovered that a lower friction effect of about 3%
can be gained by lowering the CCS viscosity.
Friction reduction
rate (%)
Base = base oil
Fuel economy
High
-30°C
CCS viscosity
(mPa·s)
Low
150°C HTHS viscosity (mPa·s)
Figure 2.1-1
Base oil 5W-30
Impact of Viscosity Characteristic on Fuel Economy
These results are organized in Figure 2.1-2. It can be seen that at 80°C there is a linear
relationship between HTHS viscosity and low friction, but even at this same HTHS viscosity, fuel
economy is high when the CCS viscosity is low. This difference suggests that on the lubricated
surfaces inside a practical engine, the shear conditions are more severe than in measurement
of a HTHS viscosity and that an even higher fuel economy could be gained with alternative
formulation technology for base oil or viscosity index improver.
Friction reduction
rate at 80°C oil
temperature (%)
80°C HTHS viscosity
Figure 2.1-2
Test Oil Viscosity Characteristic vs Fuel Economy
Next, Figure 2.1-3 shows the results of investigation of the impact of elemental phosphorus
content in oil on fuel economy. The elemental phosphorus content in test oil originates from
the ZnDTP of anti-wear additive, but it was found that there is a good low friction performance
when the elemental phosphorus content in oil is low, and such a result was unexpected.
5
Friction reduction
ratio (%)
OW-20 oil
Oil temperature
100°C
Phosphorus volume in oil
0.050 (test oil 7)
0.075 (test oil 6)
0.100 (test oil 8) = REO
Engine speed (r/min)
Figure 2.1-3
Impact of Phosphorus Elemental Volume in Oil on Fuel
Economy
This suggests that a reduction of the elemental phosphorus content in engine oil not only
curtails the catalyst poisoning of automobile emissions reduction catalyst, but also will serve as
an effective formulation technology for improving fuel economy in the future.
Next, in order to investigate the impact of friction modifier on fuel economy, four types of friction
modifier (A to D) were added to test oil 6, and the fuel economies of test oils 6A to 6D were
evaluated. It was clarified that all the friction modifiers support favorable fuel economy (Figure
2.1-4). Accordingly, it was decided, as described in the next section (Figure 2.2-2), to
investigate the impact of friction modifiers A and B, which among all the friction modifiers
exhibited favorable performance, on wear protection.
Friction reduction
ratio (%)
REO: test oil 6
Added FM
Engine speed (r/min)
Figure 2.1-4
2.2
A (test oil 6A)
B (test oil 6B)
C (test oil 6C)
D (test oil 6D)
Impact of Friction Modifier on Fuel Economy
Evaluation of Test Oil Wear Protection
In order to investigate the possibilities of reducing chlorine content in oil of ultra-low viscosity,
the wear protection of test oils 10, 12, 13 and 14 were evaluated using the JASO VTW test
method.
6
HTHS viscosity: 2.10 mPa·s
CCS viscosity: 3000 mPa·s (-35°C)
Viscosity grade: 0W-10
Phosphorus content: 0.050 mass%
Test oil 10
Cam nose
wear (µm)
Test oil 13
Test oil 12
Wear protection
Poor
Test oil 14
Good
Dispersant A (80 ppm)
Sulphonate
detergent
(70 ppm)
Figure 2.2-1
Salicylate
detergent
(less than 5 ppm)
Dispersant B (less than 5 ppm)
* Figures in parenthesis denote chlorine
content.
Impact of Chlorine in Engine Oil on Wear Protection
In test oil 13 , the dispersant (dispersant A) included in REO was replaced with dispersant B,
which has the same molecular weight and molecular structure as dispersant A but has a lower
quantity of chlorine impurities because it is obtained by a different production process. As a
result (Figure 2.2-1), upon evaluation of the anti-wear performance it was clarified that there is
no impact on wear protection performance.
On the other hand, in test oil 10, containing a sulphonate detergent, when this detergentwas
replaced with a salicylate, wear protection is improved. This was an unexpected result.
The reason does not lie in the fact that there is a direct impact from the chlorine included in
detergent. Rather it is due to the fact that the structure itself of the detergent exerts an impact
on wear protection. Furthermore, the use of salicylate offers the advantage of making it
possible to reduce the chlorine content in engine oil while also reducing the sulfur content.
Consequently, it is expected to become a promising formulation technology for gasoline engine
oil in the future.
The next subject of investigation was the impact of friction modifier on wear protection (Figure
2.2-2). In the case of test oil 10, in which there was sulphonate, wear protection was improved
by friction modifier A, but worsened by friction modifier B. In the case of test oil 14, containing
salicylate, wear protection was worsened by both friction modifiers A and B. It was thus
clarified that the impact of friction modifier on wear protection varies with the type of detergent.
Cam nose
wear
(µm)
HTHS viscosity: 2.10 mPa·s
CCS viscosity: 3000 mPa·s (-35°C)
Viscosity grade: 0W-10
Phosphorus quantity in oil: 0.050 mass%
Test oil 10
Wear
protection
Poor
Test oil 14
Sulphonate detergent
Good
Salicylate detergent
Friction
modifier
absent
Figure 2.2-2
Friction
modifier A
Friction
modifier B
Impact of Friction Modifier on Wear Protection
7
2.3
Evaluation of High-temperature Oxidation Stability in Test Oil
Of the test oils introduced thus far, test oil 14, of outstanding fuel economy and wear protection,
has been evaluated for high-temperature oxidation stability in practical engine by means of the
JASO high-temperature oxidation stability test method.
40°C
Kinematic
viscosity
Viscosity
increase rate
(%)
Duration
Figure 2.3-1
Viscosity Changes in High-temperature Oxidation Stability
Tests
The results of change in test oil viscosity are shown in Figure 2.3-1. Although this viscosity
shifted with no special problems for up to 48 hours, after 64 hours a sharp rise in viscosity was
observed, probably due to oxidation deterioration. The rate of increase in viscosity 96 hours
after testing reached up to 250%, and because this percentage is considered an index of
practical performance, it became evident that test oil 14 does not exhibit adequate performance
in terms of high-temperature oxidation stability.
Following disassembly of the engine upon completion of the test, although there were no special
problems with the cylinder liner or piston rings, damages were noted on the metal of the
crankshaft fourth slide bearing. Measurements of oil consumption volume in this engine test
(Figure 2.3-2) revealed that there was a dramatic increase in oil consumption at 64 hours.
In light of findings thus far, it can be expected that when the oil consumption volume per hour
exceeds 4 g/hr, there will be a high probability that abnormal wear is generated inside the
engine. For this reason it is suspected that some type of damage began at around 64 hours.
In addition, measurements of wear metal components in the used oil (Figure 2.3-3) suggest that
the sliding components employing aluminum material became worn, followed by the copper
material at the bearing base layer, so that copper and lead (approx. 10 ppm) dissolved into the
oil.
8
Test oil 14
Average oil
consumption
Salicylate
Duration
Figure 2.3-2
Oil Consumption in High-temperature Oxidation Stability
Tests
Worn metal
quantity in oil
Duration
Figure 2.3-3
Worn Metal Quantity in Oil in High-temperature Oxidation
Stability Tests
The vaporization characteristic of test oil 14 was measured by the NOACK test method and
found to be 15%. It was found to have a vaporization resistance characteristic in no way
inferior to that of oil on the market. In other words, the reason for the large oil consumption
volume was not simply vaporization characteristic at high oil temperature. It was also due to
mechanical factors (mechanical loss) following leakage of lubricant oil from sliding surfaces due
to ultra-low viscosity; for example, oil increases at cylinder liners and oil decreases at air supply
and exhaust valves.
Given the aforesaid points, the results of the latest engine tests indicate that engine oil of
ultra-low viscosity worsens performance in terms of high-temperature oxidation stability and that
a formulation technology is required for establishing outstanding high-temperature oxidation
prevention performance and oil film preservation performance in ultra-low viscosity oil. This
point becomes an issue for study from the year 2001.
2.4
Evaluation of Detergency of Test Oil
The JASO detergency test method was used to evaluate the detergency of test oil 14 in a
practical engine, as in the case of high-temperature oxidation stability test. The quantity of
sludge adhering to rocker cover 300 hours after testing was assessed and the results given in
Figure 2.4-1 were obtained.
9
Rocker cover
sludge rating
(10 = best)
Detergency
Good
Poor
REO (5W-30 oil on the market)
Figure 2.4-1
Detergency Test Results
Comparison of data produced by the commercial oil on the market, with those developed for this
project are presented in Figure 2.4-1. These results suggest that the detergency of test oil 14
worsens dramatically after 300 hours. Moreover, because a detergency score of 8.9 or above
after 300 hours is taken as an index of practical performance, it became evident that test oil 14
did not qualify. In addition, whereas the oil consumption volume per hour was 1.0 g/hr for oil
on the market, it was extremely large at 1.8 g/hr for the test oil. As mentioned in the previous
section, the NOACK of test oil 14 is in no way inferior to that of oil on the market, and because
the lubricant oil temperature during implementation of the engine test was limited to the low and
medium temperature ranges, it is believed that mechanical lossesdue to the ultra-low viscosity,
rather than vaporization volume, are the main causes of increased oil consumption. Moreover,
because of low viscosity, the seal property worsened due to lubricant oil at the cylinder liner,
and blow-by gas volume increased. There was also a large volume of oil consumption, and
points such as these suggest that sludge production may have been promoted.
In light of the aforementioned, the results of the latest engine test suggest that engine oil of
ultra-low viscosity leads to a decline in detergency. Moreover, for ultra-low viscosity oil, a
formulation technology is required for inhibiting the formation of sludge and for preventing its
growth once sludge has formed. These issues will be taken up from the year 2001.
2.5
Analysis of Petroleum Product Additive
In order to assess the mutual interactions in lubricant oil of the detergent, Anti-wear additive and
dispersant found in test oil 14, the Zeta potential of these agents individually and in combination
in a non-polar solvent were measured. It was found that the detergent and Anti-wear additive
each have a positive Zeta potential and that this potential is also positive when these agents are
combined. On the other hand, the Zeta potential of dispersant was found to be negative;
normally, it is also negative when dispersant is combined with other additives. This suggests
that the additives in lubricant oil mutually interact and that the behavior of electrical charge in
additives dissolved in oil is influenced by dispersant. In the future, the impact of additive type
and molecular structure on mutual interactions will be investigated, and relationships with the
fuel economy and wear protection of test oil will be examined.
10
3.
Results of Empirical Research
3.1
Evaluation of Fuel Economy
From an investigation of the effect on fuel economy of HTHS viscosity, CCS viscosity and
phosphorus content, the following points became clear.
(1)
By lowering HTHS viscosity in increments of 0.5 mPa·s, a low friction effect of about 3%
was measured. The relationship between HTHS viscosity and fuel economy is
well-known, but in the present research, it was clarified that fuel economy is high even
when the HTHS viscosity is in the ultra-low region of 2.1 mPa·s.
(2)
It was discovered that a lower friction effect of about 3% can be gained by lowering the
CCS viscosity.
(3)
Even at the same HTHS viscosity, fuel economy was found to be high when the CCS
viscosity is low. This suggests that on the lubricated surfaces inside a practical engine,
the shear conditions are more severe than in a HTHS viscosity measurement and that an
even higher fuel economy could be gained with alternative formulation technology for
base oil or viscosity index improver.
(4)
Outstanding low friction performance was manifested when the elemental phosphorus
content in oil, that is the ZnDTP allocation volume, was low. This suggested that a
reduction of the phosphorus content in engine oil not only curtails the catalyst poisoning,
but will also be effective in improving fuel economy.
(5)
In the latest evaluation, favorable fuel economy was demonstrated for all the friction
modifiers.
3.2
Evaluation of Wear Protection of Test Oils
In order to investigate the possibilities of reducing chlorine content in oil, anti-wear
performances of four test oils were evaluated using the JASO VTW test method, and the
following points were clarified.
(1)
With respect to dispersant, it was clarified that there is no impact on wear protection even
when using a dispersant that has a low quantity of chlorine impurities because of a
different production process.
(2)
When a sulphonate was replaced with a salicylate, wear protection was improved. The
reason does not lie in the fact that there is a direct impact from the chlorine included in
detergent. Rather it is due to the structure itself of the detergent. Moreover, the use of
salicylate offers the advantage of making it possible to reduce the chlorine content in oil
while also reducing the elemental sulfur content in oil.
It was also clarified that the impact of friction modifier on wear protection varies with the type of
detergent.
11
3.3
Evaluation of High-temperature Oxidation Stability of Test Oils
Of the test oils introduced thus far, a test oil (0W-10) of outstanding fuel economy and wear
protection was evaluated for high-temperature oxidation stability by means of the JASO
high-temperature oxidation stability test method. The results suggest that engine oil of
ultra-low viscosity worsens performance in terms of high-temperature oxidation stability and that
a formulation technology is required for establishing outstanding high-temperature oxidation
prevention performance and oil film preservation performance in ultra-low viscosity oil.
3.4
Evaluation of Detergency of Test Oil
The JASO detergency test method was used to evaluate the detergency of test oil (0W-10), as
in the case of high-temperature oxidation stability test. The results suggest that engine oil of
ultra-low viscosity leads to a decline in detergency. Moreover, for ultra-low viscosity oil, a
formulation technology is required for inhibiting the formation of sludge and for preventing its
growth once sludge has formed.
3.5
Analysis of Additive for Lubricants
The Zeta potentials of detergent and anti-wear additive are positive, while that of dispersant was
found to be negative. Normally, it is also negative when dispersant is combined with other
additives. This suggests that the additives in lubricant oil mutually interact and that the
behavior of electrical charge in additives dissolved in oil is influenced by dispersant.
4.
Synopsis and Future Issues
4.1
Research on Formulation Technology for Improving Wear Protection and Fuel
Economy
Figure 4.1-1 summarizes the formulation technologies obtained up to the year 2000 for
achieving ultra low viscosity in gasoline engine oil. As indicated by the arrows in the figure, the
targets of the present research project over 4 years call for outstanding fuel economy while
wear protection is maintained at its current performance level. At present, however, there is
still no formulation technology to match this objective. In 2001, the formulation technologies
obtained thus far will be combined and optimized, and ash-free supplementary additives having
no sulfur content but offering both fuel economy and wear protection will be sought out by
means of vehicle-mounted engine wear tests and friction/ wear testers. In 2000, fuel economy
was evaluated by means of vehicle-mounted motoring friction test, and in 2001, fuel economy
will be evaluated using practical vehicles. The correlation among results obtained thus far will
be investigated and research will be conducted for further improvement of fuel economy.
12
Fuel economy
Lowering HTHSV
Project objective
Elemental technologies to be
investigated from 2001:
Improvement of fuel economy and
of wear protection under conditions
of mixed lubrication
Lowering CCS
Reduction of
ZnDTP
Salicylate detergent
Wear protection
Figure 4.1-1
4.2
Outline of Formulation Technology Obtained up to this
Fiscal Year and Future Indexes
Improvements in Detergency and High-temperature Oxidation Stability
From an investigation of the impact of ultra-low viscosity in engine oil on detergency and on
high-temperature oxidation stability, which was conducted in 2000 using a practical engine, it
was found that ultra-low viscosity worsens performance in cleaning and in high-temperature
oxidation stability. In the year 2001, formulation technologies for improving these
performances will be researched.
4.3
Analysis of Engine Oil Additives
In fiscal year 2000, the mutual interactions of additives for lubricants included in engine oil could
be measured by analyzing Zeta electric potential. In 2001, more accurate measurements of
mutual interactions will be taken, including the impacts of additive type and molecular structure;
associations with the performance of practical lubricant oils will be investigated, together with
the relationships between mutual interactions and lubricant oil deterioration.
Reference Bibliography
1.
Kouichi Kubo, “Preprinted Issues of the Japan Automobile Technology Association”
932, 137-140 (1993-5)
2.
T.Fujitsu, at. El, SAE Technical Paper Series No.981445 (1998)
3.
Minoru Kibukawa, “Tribologist”, 41 (3), 203-208 (1996)
Copyright 2001 Petroleum Energy Center all rights reserved.
13