High quality gear oils must lubricate, cool and protect geared systems.
They must also carry damaging wear debris away from
contact zones and muffle the sound of gear operation.
Commonly used in differential gears and standard transmission
applications in commercial and passenger vehicles, as
well as a variety of industrial machinery, gear oils
must offer extreme temperature and pressure protection
in order to prevent wear, pitting, spalling, scoring,
scuffing and other types of damage that result in equipment
failure and downtime. Protection against oxidation,
thermal degradation, rust, copper corrosion and foaming
is also important.
AMSOIL submitted its 75W-90 Synthetic Gear Lube (AGR)
and Valvoline 75W-90 Gear Lube to an independent laboratory for
quality comparison tests. The gear lubes were tested according to
ASTM testing procedures in several critical performance areas, including
oxidation resistance, viscosity retention and cold temperature fluidity.
Oxidation resistance was measured using the L-60-1 Thermal Oxidation
Stability Test, viscosity retention was measured using the KRL Shear
Stability Test and cold temperature fluidity was measured using
the Brookfield Viscosity Test. Additional load carrying, wear, extreme
pressure and scoring protection tests were performed exclusively
on AMSOIL 75W-90 Synthetic Gear Lube using the L-37 High Torque
Axle Test and the L-42 High Speed Axle Test.
L-60-1 Thermal Oxidation Stability Test
Test Conditions
The L-60-1 Thermal Oxidation Stability Test measures a lubricant's
rate of deterioration under severe oxidation conditions. A measured
sample of test lubricant is placed in a special gear case with two
spur gears and a copper catalyst strip. The gears are driven at
1,725 rpm at 163°C for a 50-hour duration, while air is bubbled
through the sample.
Viscosity increase, deposits not soluble in pentane
or toluene, carbon varnish and sludge deposits are measured upon
test completion. Test specifications are listed below.
L-60-1 Thermal
Oxidation Stability Test Specifications
|
|
API GL-5 |
API MT-1/SAE J-2360/
MIL-PRF-2105E/Mack GO-J |
Mack GO-J+ |
Test Conditions |
50 hours @ 163°C |
50 hours @ 163°C |
100 hours @ 163°C |
Viscosity Rise, % |
100 Max. |
100 Max. |
100 Max. |
Pentane Insolubles, % |
3 Max. |
3 Max. |
3 Max. |
Toluene Insolubles, % |
2 Max. |
2 Max. |
2 Max. |
Carbon Varnish, rating |
Not required |
7.5 Min. |
7.5 Min. |
Sludge, rating |
Not required |
9.4 Min. |
9.4 Min. |
L-60-1 Thermal
Oxidation Stability Test Results
|
|
AMSOIL Synthetic
75W-90 |
Valvoline
75W-90 |
Valvoline
75W-90 |
Test Conditions |
100 hours @ 163°C |
50 hours @ 163°C |
100 hours @ 163°C |
Viscosity Rise, % |
25.17 |
17.50 |
38.50 |
Pentane Insolubles, % |
0.20 |
0.87 |
1.17 |
Toluene Insolubles, % |
0.13 |
1.11 |
0.99 |
Carbon Varnish, rating |
8.0 |
7.2 |
5.9 |
Sludge, rating |
9.5 |
9.4 |
9.4 |
Test Results
Because AMSOIL 75W-90 Synthetic Gear Lube is a premium lubricant
designed for extended drain service, the test was allowed to continue
for 100 straight hours, double the standard test length. The Valvoline
75W-90 was run at both the standard 50-hour test length and the
double 100-hour test length. Test results indicate AMSOIL 75W-90
Synthetic Gear Lube outperformed Valvoline at both test lengths.
Even at double the standard test length, AMSOIL 75W-90
scored almost four times better than industry test specifications
in the area of viscosity increase, while also greatly exceeding
specifications in all areas of the test.
The photographs below show the superior deposit-control
characteristics of AMSOIL 75W-90 Synthetic Gear Lube.
L-60-1 Thermal Oxidation Stability Test
Results
|
AMSOIL 75W-90 (100
hours)
|
Valvoline 75W-90
(100 hours)
|
Valvoline 75W-90
(50 hours)
|
|
|
Even after enduring a
double-length, 100-hour L-60-1 Thermal Oxidation Stability Test,
AMSOIL 75W-90 Synthetic Gear Lube produced significantly fewer
deposits than the Valvoline 75W-90 run at a standard, 50-hour
test. |
KRL Shear Stability Test
Test Conditions
It is essential that high-quality gear lubes resist shear to ensure
adequate oil film thickness and protection against friction and
wear. The KRL Shear Stability Test is used to determine the mechanical
shear stability of lubricants containing polymer. Mandatory under
the SAE J-306 gear oil standard, the KRL Shear Stability Test makes
use of a taper roller bearing in order to shear the test fluid and
determine the permanent drop in viscosity caused by the mechanical
stress under practical conditions. Under the specifications of SAE
J- 306, the measured viscosity at 100°C (212°F) of an SAE
90 gear oil must exceed 13.5 cSt after 20 hours of testing.
Test Results
AMSOIL 75W-90 Synthetic Gear Lube easily exceeded SAE J-306 specifications
following the 20-hour test length and was allowed to continue for
a total of 192 straight hours, almost 10 times longer than the standard
test length. Even after this extended test, AMSOIL 75W-90 lost only
0.40 percent of its original viscosity, making it 99.6 percent shear
stable.
Valvoline 75W-90 Gear Lube, on the other hand, failed
the test during the initial 20-hour testing period, losing 14 percent
of its original viscosity.
Brookfield Viscosity Test
Test Conditions
The Brookfield Viscosity Test (ASTM 0-2983) is used to determine
the internal fluid-friction of a lubricant during cold temperature
operation. The lubricant sample is chilled in a -40°C (-40°
F) air bath for 16 hours, and a Brookfield viscometer determines
the torque required to shear the lubricant. The lower the cold temperature
viscosity (measured in centipoise), the better the cold temperature
protection. ASTM specifications dictate that 75W-90 gear oils measure
less than 150,000 cP at test completion.
Test Results
AMSOIL 75W-90 Synthetic Gear Lube easily passed the Brookfield Viscosity
Test, measuring 88,000 cP at test completion, 42 percent less than
test limits. The superior cold temperature properties of AMSOIL
75W-90 Synthetic Gear Lube ensure quicker oil flow, enhanced component
protection and improved fuel efficiency.
Many conventional lubricants fail to pass the Brookfield
Viscosity Test due to the paraffinic (wax) content in their base
oils. Valvoline Gear Lube passed the test at 130,000 cP, only 13
percent lower than test limits.
KRL Test Results |
AMSOIL 75W-90
(After 192 hrs. KRL) |
Valvoline 75W-90
(After 20 hrs. KRL) |
Beginning Viscosity @ 100°C (cSt) |
15.09 |
14.46 |
Ending Viscosity @ 100°C
(cSt) |
15.03 (pass) |
12.42 (fail) |
% Viscosity Loss, 100°C |
0.40% |
14.10% |
1-37 High Torque Axle Test
|
The gears protected by AMSOIL 75W-90 Synthetic
gear Oil showed little or no rippling, ridging, pitting or deposits
following the L-37 High Torque Axle Test. |
Test Conditions
The L-37 High Torque Axle Test is used to evaluate a gear lubricant's
load-carrying, wear and extreme pressure characteristics in hypoid
gears operating under both high-speed/low-torque and low-speed/high-torque
conditions. A Dana Model 60 hypoid gear axle is used with either
coated or uncoated drive gear and pinion to drive two dynamometers
from an eight-cylinder, 5.7-liter gasoline engine. With the axle
filled with the test lubricant, the high-speed/low-torque test is
performed for 100 minutes, with the gears visually assessed afterwards.
Next, the low-speed/high-torque test is run for 24 hours, followed
by a thorough inspection of the gears. Performance relative to API
GL-5 and MIL-PRF-2105E specifications is assessed based on tooth
surface rippling, ridging, pitting and wear, deposits and discoloration.
Test Results
Testing on AMSOIL 75W-90 Synthetic Gear Oil was conducted using
uncoated gear and pinion. The AMSOIL lubricant passed on all counts
and showed little to no rippling, ridging, pitting or deposits,
indicating that AMSOIL 75W-90 provides superior protection and performance
under extreme pressure conditions.
L-42 High Speed Axle Test
Test Conditions
The L-42 High Speed Axle Test evaluates the antiscoring characteristics
of a gear lubricant operating under high-speed and shock-loading
conditions. A Spicer Model 44-1 hypoid gear axle is driven by a
5.7 liter, V8 gasoline engine with a four-speed truck transmission
and two high-inertia dynamometers and hard accelerated to 100 mph.
The axle is periodically shock-loaded through a dynamometer to simulate
high shock-loading conditions. The axle is accelerated through the
gears to 1,050 r/min and decelerated to 530 r/min. This cycle is
repeated five times, followed by 10 shock loadings. In order to
meet API GL-5 and MIL-PRF-2105E gear oil specifications, scoring
must be equal to or better than gears tested with a reference oil.
Test Results
AMSOIL 75W-90 Synthetic Gear Oil easily passed the L-42 High
Speed Axle Test, receiving a significantly better rating than
the reference oil and leaving little to no scoring on the
ring and pinion.
L-42 High
Speed Axle Test
|
|
AMSOIL 75W-90
|
Reference Oil
|
Ring |
13
|
19
|
Pinion |
18
|
27
|
|
|
The gears protected by AMSOIL
75W-90 Synthetic gear Oil showed little to no scoring following
the L-42 High Speed Axle Test. |
|