SAE TECHNICAL
PAPER SERIES
2007-01-3987
Comparison of OEM Automatic Transmission
Fluids in Industry Standard Tests
Roy Fewkes and Angela Willis
General Motors Corp.
Powertrain & Fluid Systems
Conference & Exhibition
Rosemont, Illinois
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Printed in USA
2007-01-3987
Comparison of OEM Automatic Transmission Fluids in
Industry Standard Tests
Roy Fewkes and Angela Willis
General Motors Corp.
Copyright © 2007 SAE International
ABSTRACT
As a result of raised awareness regarding the
proliferation of individual OEM recommended ATFs,
and discussion in various forums regarding the
possibility of ‘universal’ service fill fluids, it was decided
to study how divergent individual OEM requirements
actually are by comparing the fluids performance in
industry standard tests.
A bench-mark study was carried out to compare the
performance of various OEM automatic transmission
fluids in selected industry standard tests. All of the fluids
evaluated in the study are used by certain OEMs for
both factory and service fill. The areas evaluated
included friction durability, oxidation resistance, viscosity
stability, aeration and foam control. The results of this
study are discussed in this paper. Based on the results,
one can conclude that each ATF is uniquely formulated
to specific OEM requirements. In addition, the results
show that a customer should not deviate from the
automatic transmission fluid specified in the vehicle's
owners manual.
INTRODUCTION
In recent years, a number of factors, including changes
in automatic transmission design, materials, and
controls systems, have led many OEMs to implement
revisions to their ATF specifications. The main ATF
performance areas affected by these revisions are:
 Viscometrics and related properties

 Thermal and oxidative stability
 Anti-wear performance
 Friction characteristic and durability
 Aeration and Foam performance
A range of commercially available automatic
transmission fluids were tested in order to compare their
performance in terms of the above referenced
properties. The tests that were selected for this
evaluation are all currently used in OEM specifications.
However, they are not necessarily used in each
specification represented by the individual OEM fluids
that are a part of this evaluation. The fluids tested are, at
the time of writing, all used as an OEM factory and
service fill. The test results showed a considerable
variance in the performance of the fluids despite their
conformity with individual OEM ATF specifications.
When latest transmission developments are
considered, it becomes clear that there is, in many
instances, an increasing divergence of performance
requirements. The paper examines and compares the
individual fluids and the level of compromise required if
a common fluid was desired.
RESULTS AND DISCUSSION
GENERAL PROPERTIES
Some general physical and chemical properties were
evaluated on each of the seven fluids. Those properties
consist of viscometrics, acidity, volatility/flammability,
and elemental chemistry composition. Table 1 gives an
illustration of those results.
Fluid A
Kinematic
Viscosity,
2
mm /s
Brookfield
Viscosity,
mPa.s
Cold Crank
Simulation,
mPa.s
Total Acid
Number,
mg
KOH/mL
Flash
PointPMCC, oC
Elemental
Analysis,
ppm
29.79
5.99
Fluid
B
35.00
7.54
Fluid
C
27.23
5.71
Fluid
D
29.53
7.22
Fluid
E
24.17
5.60
Fluid
F
35.13
7.98
Fluid
G
36.99
7.40
-40°C
11,500
9,980
9,750
5,480
8,340
9,750
7,920
-30oC
3,300
2,660
2,600
2,320
2,440
2,510
2,940
0.6
0.8
0.6
0.3
1.0
0.7
1.1
184
160
196
170
170
166
200
0
0
88
63
5
0
203
7
0
1400
2
0
0
140
672
1
0
460
3
5
1600
2
0
0
134
555
16
0
386
3
7
1990
18
0
0
315
356
226
0
2
7
3
770
365
0
0
71
111
0
0
273
3
2
670
1
0
0
96
44
3
0
235
1
1
1000
7
0
0
71
26
0
0
304
2
3
150
0
40°C
100°
C
Al
Ba
B
Ca
Mg
Mn
P
Si
Na
S
Zn
Table 1. General Properties of the Seven OEM Fluids
Note that whilst several of the fluids, namely A, C, and E,
follow a more modern trend in terms of viscometrics (i.e.
blended KV 100oC between 5.5-6.0 mm2/s), where as
the others follow an older conventional trend (all blended
to a KV 100oC of 7.0-7.5 mm2/s). Brookfield
viscosities[1] at -40oC, four fluids B, C, and F appear to
be relatively similar with Fluid A having the highest
Brookfield viscosity. The fluid with the lowest measured
Brookfield was fluid D. Brookfield viscosity
measurements will tend to vary due to both test
repeatability and batch-to-batch variation for a given
fluid. The differences between these fluids, except fluid
D, could very well be within the window this type of
variance. One interesting note, the viscosities measured
for cold crank [2] at -30oC did not differ with each fluid
nearly as much as the Brookfield measurements. For
example, Fluid D had a similar performance in cold
crank as Fluid E, however, the Brookfield viscosities
differed (Fluid D Brookfield at - 40oC was 5,480 mPa.s
and Fluid E Brookfield at -40oC was 8,340 mPa.s) This
data shows that depending on the concern Brookfield
viscosity may not always be a good indicator of low
temperature, viscometric performance. In addition to
viscometrics, elemental analysis[3] and total acid
numbers[4] illustrate that there are several formulation
approaches used in order to produce a fluid meeting
specific OEM needs. Taking the method repeatability
into account, total acid numbers are similar in Fluids A,
B, C, and F. Fluids E and G have a higher acid number
than the others. Flash points[5] seem generally similar;
however, Fluids B and F have lower flash points than
the other fluids. Again, the data for all of these
characteristics indicate differences in formulation
philosophies and OEM needs. Based on this data alone,
the “one-size-fits -all” philosophy in terms of automatic
transmission fluid does not seem to be possible.
CORROSION
Table 2 shows corrosion/rust results on the seven
OEM fluids. The standard ASTM D1748 and D130 test
methods were followed to evaluate this property.
Fluid
A
Fluid
B
Fluid
C
Fluid
D
Fluid
E
Fluid
F
Fluid
G
Pass
Pass
Pass
Pass
Fail
Pass
Pass
1B
2C
1B
1B
2A
1B
1B
D 1748
Rust
D 130
Corrosion
Table 2. Corrosion Data from Seven OEM Fluids
ASTM D1748 [6] is a method in which one hangs clean
and polished steel panels, coated with each of the test
oils, in a humidity chamber for a given period of time at
48.9 + oC. Panels are rated on pass/fail criteria. Per the
method, a pass constitutes a panel having no more than
three dots of rust, each one no larger than 1 mm in
diameter. A fail constitutes a panel having four or more
dots of rust, of any size, or having one or more dots with
a diameter greater than 1 mm. Referring back to Table
2, using the above reference criteria, all but Fluid E
would be deemed to be a pass.
The other method used was ASTM D130 [7], or known
as the copper strip corrosion test. This test uses a clean
and polished copper strip, submerged in test oil, and
placed in a pressurized vessel then heated to 150oC for
3 hours. Copper strips are then inspected and classified
using the classifications noted in the ASTM method.
OEMs may have different limits in terms of
classifications. This could be due to the amount of
copper or type of copper alloys used in their
transmissions. Most OEMs’ specifications require a limit
of 1B. Referring to Table 2, all but two fluids, B and E,
would have met this limit.
Classification
Designation
1
Slight Tarnish
2
Moderate Tarnish
Description
a.
b.
a.
b.
c.
d.
e.
3
Dark Tarnish
a.
b.
4
Corrosion
a.
b.
c.
Light orange, almost the same
as freshly polished strip
Dark Orange
Claret red
Lavender
Multicolored with lavender blue
or silver, or both, overlaid on
claret red
Silvery
Brassy or gold
Magenta overcast on brassy
strip
Multicolored with red and green
showing, but no gray
Transparent black, dark gray or
brown with peacock green
barely showing
Graphite or lusterless black
Glossy or jet black
Table 3. Copper Strip Classifications per ASTM D130
SHEAR STABILITY
Shear stability was evaluated using the KRL tapered
bearing test which is widely used by a number of
OEMs. The method used was CEC L-45-T-93, modified
to 40 hours. The taper bearing runs submerged in 40
mL of fluid at a constant speed and load at 60 oC for a
given period of time, in this case, 40 hours. The data is
presented in Figure 1, Figure 2, and Table 4.
Initial KV
100°C
Final KV
100°C
%
Viscosity
Loss
Fluid A
Fluid B
Fluid C
Fluid D
Fluid E
Fluid F
Fluid G
5.99
7.48
5.71
7.22
5.60
8.00
7.40
5.61
5.97
5.44
5.67
5.15
5.88
7.01
6.3
20.2
4.7
21.5
8.0
26.5
5.3
Table 4. KRL Test Data Comparison Between the
Seven OEM Fluids
9.00
Initial KV 100C
Final KV 100C
8.50
8.00
KV,
mm2/s
7.50
7.00
6.50
temperature. For this evaluation, the temperature these
fluids were tested at was 180oC. Kinematic viscosities
and total acid numbers were measured before and
after test on each fluid. In addition, subjective ratings to
quantify fluid oxidation include flask photographs and
blotter spot tests in order to visually check dispersancy.
The results from this test on the seven fluids are
illustrated in Figures 3, 4, and Table 5.
Fluid
A
Fluid
B
Fluid
C
Fluid
D
40 C
4.1
23.5
28.3
100 C
4.0
18.8
23.0
0.6
1.5
1.0
6.00
5.50
KV,
mm2/s
5.00
TAN,
mg
KOH/g
4.50
4.00
Fluid A
Fluid B
Fluid C
Fluid D
Fluid E
Fluid F
Fluid G
Fluid
E
Fluid
F
Fluid
G
41.0
2.5
38.4
0.8
35.1
-0.4
31.3
1.4
1.9
0.5
2.3
1.2
Table 5. Data from DKA Oxidation Test on the Seven
OEM Fluids
Figure 1. Initial and Final Kinematic Viscosities at 100oC
on Seven OEM Fluids from KRL testing
Delta KV at 100C
Delta TAN
80.0
2.5
70.0
30.00
2.0
60.0
KV, mm2/s
% Viscosity Loss
25.00
20.00
50.0
1.5
40.0
1.0
30.0
15.00
20.0
0.5
10.00
10.0
5.00
0.0
0.0
Fluid A
0.00
Fluid A
Fluid B
Fluid C
Fluid D
Fluid E
Fluid F
Fluid G
Fluid B
Fluid C
Fluid D
Fluid E
Fluid F
Fluid G
Figure 3. Comparison of Seven OEM Fluids Using KV
and TAN from DKA Oxidation Test
Figure 2. % Kinematic Viscosity Loss on Seven OEM
Fluids from KRL Testing
Results reported are for comparative purposes only and
do not attempt to illustrate a pass or fail since OEMs
requirements vary. For instance, General Motors has
established limits [8, 9] for minimum kinematic viscosity
measured at 100oC, maximum decrease in 100oC
kinematic viscosity, and minimum mean 100oC
kinematic viscosity with which the average is calculated
using the start of test and end of test viscosities. One
note of interest, with exception to fluid G, the fluids with
higher pre-test viscosities also had the highest viscosity
losses. Fluids A, C, E, and G all performed similarly.
However, fluid G had a high pre-test viscosity, but did
not shear down to the same extent as the other high
viscosity fluids.
OXIDATION
To evaluate oxidation the DKA method [10], CEC L-48A-95 was used. This test is widely used by a number of
OEMs to evaluate oxidation performance of automatic
transmission fluids and gear oils. The test can be run at
various temperatures and test duration depending on
individual OEM requirements. The standard test
involves bubbling 5 L/min of air through 100 mL of test
fluid in a tall-form beaker for 192 hours at a given
Figure 4. Comparison of DKA Flasks (Fluids A-G, left
to right)
Fluid D has the highest change in kinematic viscosity at
100oC. Fluid E appears that it performed well, with a delta
KV of -0.4 mm2/s and a delta TAN of 0.5 mg KOH/g.
However, actually what has occurred was that the viscosity
modifier was thermally sheared even though
the fluid was not substantially oxidized. In this test, fluids
B, C, D, and F, all showed some significant increase in
KV 100C. Noting the DKA flasks, in Figure 4, Fluid A
had only a slight varnish present. However, it should be
noted that various OEMs use different tests to evaluate
oxidation performance which could effect the fluid
differently. Therefore, the results presented are for
comparative purposes only and are not intended to
illustrate pass or fail.
Temperature, oC
Fluid A
Fluid B
Fluid C
Fluid D
Fluid E
Fluid F
Fluid G
60
80
100
120
101.3
91.7
88.3
79.8
87.7
86.1
107.9
65.5
55.7
51.8
47.8
53.7
54.2
64.1
45.7
37.6
35.5
31
37.7
34.2
43.5
35.2
26.4
24.1
21.6
29
24.5
28.4
Table 6. Film Thickness, in Nanometers, Measured at 1
m/s Entrainment Speed
ANTI-WEAR PERFORMANCE
The anti-wear performance of the seven fluids were
evaluated using the FZG Load Stage Test A/8.3/90
which is ASTM D 5182. Results are shown in Figure 5.
120
Fluid A
Fluid B
100
Film thickness, nm
Fluid C
14
Load Stage Passed
12
10
Fluid D
Fluid E
80
Fluid F
Fluid G
60
40
8
20
6
0
4
50
70
90
110
130
Temperature, ˚C
2
0
Fluid A
Fluid B
Fluid C
Fluid D
Fluid E
Fluid F
Fluid G
Figure 5. FZG Load Stage Comparison Between Seven
OEM fluids.
Being that the error of the test is + 1 load stage, Fluids
A, B, C, F, and G are fairly similar in performance, with
fluids B and F being slightly better. Fluid D had the
lowest load stage passed which was 7. This data really
emphasizes the different needs of OEMs. For example,
some OEMs may use different gear and shaft materials
and processing methods which requires less emphasis
on the need for a fluid to have high anti-wear
performance. Another example is that some OEMs
target their portfolio towards more low torque, low load
applications, where others have a more diverse portfolio
which includes high torque, high speed performance,
and high load applications.
Another contributor to anti-wear performance is film
thickness. To evaluate this, we measured
elastohydrodynamic film thickness of each fluid by
using the EHDPROC_11[8, 9, 11] at the Imperial
College located in London, England. Measurements
were made at four temperatures: 60oC, 80oC, 100oC,
and 120oC. A film of each fluid was placed on a steel
ball which was rolled onto a flat, glass contact surface.
Film thicknesses at each temperature were measured
using ultrathin film interferometry. Results generated
are shown in Figure 6 and Table 6.
Figure 6. Graph of Film Thickness Versus Temperature
on Seven OEM Fluids
Taking into account the error of the method, Fluids A
and G have the highest film thickness at 60oC and the
other fluids, with exception to Fluid D, have equivalent
film thicknesses. Fluid D had the lowest film at 60oC.
However, as temperature increases, all of the fluids
become more equivalent in film thickness. Referring
back to the viscometrics (refer to Table 1), it becomes
apparent that the bulk viscosity does not necessarily
align with film thickness. For instance, Fluid G which has
a KV100 of 7.4 mm2/s, and Fluid A with a KV100 of 5.9
mm2/s are essentially identical in film thickness.
Additionally, fluid B and fluid D have similar KV100, but
the film thickness at any given temperature is lower in
Fluid D. The one general observation to note is that film
thickness drastically decreases with increasing
temperature. This shows the criticality of keeping sump
temperatures and interface temperatures as optimal as
possible. Higher transmission sump and interface
temperatures could lead into lower film which may
increase wear in the transmission.
FRICTION PERFORMANCE
Friction performance was evaluated using the General
Motors Single Plate Test. In this test, the conditions run
were per the DEXRON®-VI specification [8, 9] using Borg
Warner 4329 material. The results shown are strictly to
compare fluid performance to this particular test. The
conditions and friction material may not represent
different OEMs requirements. Results will vary using a
different clutch material and/or different operating
conditions. Figures 7 and 8 show graphs of the data
generated on the fluids. Figure 7 shows midpoint torque
versus time. Figure 8 shows end torque versus time.
One of the DEXRON®-VI acceptance criteria is that
midpoint torque must maintain a minimum of 85 Nm
throughout the entire test duration of 200 hours. Based
on this, fluids B and C fell below the 85 Nm limit at about
25 and 80 hours respectively. One observation to note,
even though fluids D and G met the midpoint torque
criteria, they both exhibit a rooster tail characteristic
towards the end of test, which would not be desirable
(refer to end torque plot) . This data emphasizes the
need to follow the owners’ manual and only use the
OEM fluid specified.
Fluid A
Fluid B
Fluid C
110.0
Fluid D
Fluid E
105.0
Fluid F
torq
ue
(Nm)
100.0
Fluid G
Mid-point
95.0
90.0
FOAM AND AERATION PROPERTIES
The final set of properties evaluated was foam and
aeration. For foaming properties, ASTM D892 [12] was
used to test the fluids. Results are shown in Table 7.
Most of the fluids had similar performance. However,
Fluid E had slightly higher foaming tendencies in all
sequences.
Seq. I
Seq. II
Seq. III
Seq. IV
Fluid
A
0/0
0/0
0/0
30 / 0
Fluid
B
0/0
20 / 0
0/0
20 / 0
Fluid
C
0/0
10 / 0
0/0
40 / 0
Fluid
D
0/0
10 / 0
0/0
20 / 0
Fluid
E
30 / 0
40 / 0
20 / 0
30 / 0
Fluid
F
0/0
20 / 0
0/0
30 / 0
Fluid
G
0/0
10 / 0
0/0
10 / 0
Table 7. D892 Foam Results of Seven OEM fluids.
For air entrainment properties, the GM Aeration Rig Test [8,
9, 13] was used to measure each fluid. As described in SAE
2004-02- 2914, in situ Chris Morgan, Jill Cummings, Roy
Fewkes, and J. Matthew Jackson, the test apparatus is a
fluid containment box with a CVT pump, sprockets, and
chain mounted inside. With the test fluid inside the
containment box, the CVT pump runs at a given speed via
the chain and sprockets, which are spun by an electric
motor outside the containment box. Fluid inside the
containment box is allowed to go through a line to a density
measuring device, then back into the containment box. This
test is run at three different temperatures: 60oC, 90oC, and
120oC. Figure 9 illustrates the results from the test in terms
of % aeration.
85.0
Fluid A
80.0
Fluid B
25.00
Fluid C
75.0
0
50
100
150
Fluid D
200
20.00
% Aeration
Time (h)
Figure 7. Plot of Midpoint Torque v. Time Data
Fluid E
Fluid F
Fluid G
15.00
10.00
Fluid A
Fluid B
120.0
Fluid C
5.00
Fluid D
110.0
Fluid E
Fluid F
(Nm
End-torque )
100.0
Fluid G
0.00
60°C
90°C
120°C
Temperature
Figure 9. GM Aeration Test Results from Seven OEM
Fluids
90.0
80.0
70.0
60.0
50.0
0
50
100
150
200
250
Time (h)
Figure 8. Plot of End Torque v Time Data Generated
Fluid G had the lowest % aeration out of the seven
fluids. Fluids B, C, and F demonstrated similar
performance. Fluid D had the highest % aeration at
60oC, however, as temperature increased started to
perform like Fluids B, C, and F. Fluid E had the highest
% aeration at 120oC. This data further confirms the need
to follow the vehicle owner’s manual and use the fluid
specified. The data clearly shows that each fluid is
formulated to a given set of conditions, whether it is duty
cycle or transmission architectures.
CONCLUSION
Conclusions are as follows:















There are numerous additive chemistries
available and used by OEMs in factory
and service fill fluids.
The additive chemistries are, in some
cases, very different and, if mixed together,
performance is unpredictable.
The additive systems and resultant fluids are
formulated to provide appropriate performance
in conjunction with the materials used by
specific OEMs.
Not all fluids are interchangeable - using the
wrong fluid in a given application could result
in transmission damage.
Based on the wide variation of performance
shown in the test data, it would be difficult for
an universal fluid be truly be universal. As an
example, friction performance of the OEM fluids
on one friction material is so varied. However,
we know each individual OEM fluid suits the
friction materials and duty cycle of the OEM
transmissions they accommodate. In addition,
the pure aspect that the additive chemistries
are much different amongst the OEM fluids,
based on ICP elemental analysis, illustrates
that these fluids are designed for a specific set
of requirements making it difficult for one fluid
formulation to be properly balanced to
accommodate all of the differing OEM needs.
OEMs, in many cases, prioritize performance
attributes differently, depending on design
and typical operating conditions.
After examination of the analytical data, it is clear
that after-market additives can not convert one fluid
into another. On a chemistry standpoint, the fluids
are much too different for these broad aftermarket
additives to convert one to another.
It is important to use the recommended OEM
approved product for optimum performance and
durability.
REFERENCES
1. “Standard Test Method for Low-Temperature
Viscosity of Lubricants Measured by
Brookfield Viscometer”, ASTM D2983-04a.
2. “Standard Test Method for Apparent Viscosity of
Engine Oils Between -5 and -35oC Using the
Cold-Cranking Simulator”, ASTM D5293-04.
3. “Standard Test Method for Determination of Additive
Elements, Wear Metals, and Contaminants in Used
Lubricating Oils and Determination of Selected
Elements in Base Oils Selected Elements in Base
Oil by Inductively Coupled Plasma Atomic Emission
Spectrometry”, ASTM D5185-05.
4. “Standard Test Method for Acid Number of
Petroleum Products by Potentiometric
Titration”, ASTM D664-06a.
5.
“Standard Test Method of Flash Point by PenskyMartens Closed Cup Tester”, ASTM D93-06.
6. “Standard Test Method for Rust Protection by
Metal Preservatives in the Humidity Cabinet”,
ASTM D1748-02.
7. “Standard Test Method for Corrosiveness to
Copper from Petroleum Products by Copper Strip
Test”, ASTM D130-04.
8. GMN10060. General Motors Engineering
Standards, Materials and Processes – Fuels and
Lubricants. DEXRON®-VI, Automatic Transmission
Fluid. June 2005.
9. B. Calcut, R. Fewkes, A. Willis, “General Motors
DEXRON®-VI Global Service-Fill Specification”,
SAE Paper 2006-01-3242.
10. B. Calcut, R. Fewkes, “The Oxidative Stability of
GM’s DEXRON®-VI Global Factory Fill ATF”,
SAE Paper 2006-01-3241.
11. H. A. Spikes, “The Elastohydrodynamic
Film Forming Properties of Seven
Transmission Lubricants”.
12. “Standard Test Method for Foaming Characteristics of
Lubricating Oils”, ASTM D892-06.
13. J. Cummings, R. Fewkes, C. Morgan, “A New
Method of Measuring Aeration and Deaeration
of Fluids”, SAE Paper 2004-01-2914.