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TitleGear Lubrication Manual
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Total Pages10
Document Text Contents
Page 4

Viscosity

AGMA 9005-D94 Gear Oil Requirements

R&O / Worm / EP
90 minimum

Synthetic
120 minimum

AGMA No. Hours min.
1 & 2 1500
3 & 4 750
5 & 6 500

D 2270

D 445

D 665B

D 130

D 2893
Modified

24 hours in seawater

1b maximum (3hrs/250ºF)

D 943

Viscosity
Index

Oxidation
Stability

(R&O oils
only)

Oxidation
Stability

Corrosion

Rust, Sea,
H2O

AGMA
Requirements

ASTM
Number

ASTM
Test

6% maximum viscosity
increase at 250ºF

Must Meet
AGMA Grades

Table 2

Table 2 below shows a comparison between the AGMA’s mini-
mum performance standards for gear oils and the performance of
Royal Purple’s gear oils. Royal Purple lists at least two gear oils

for each AGMA classification. Every Royal Purple gear oil great-
ly exceeds AGMA’s 9005-D94 performance standards.
Note: This table spans across two pages.

ASTM D-445 determines an oil’s viscosity of fluidity at a specific temperature.
At the same temperature, a light ISO 32 oil has a lower viscosity than a heavier
ISO 150 oil. When the temperature changes, the viscosity of each oil will
change. When an oil’s temperature increases it becomes more fluid, or thinner;
When it temperature drops it becomes less fluid, or thicker. The oil temperature
must always be given when reporting a viscosity. The three most common tem-
peratures used to report viscosities are 40ºC, 100ºC and the oil’s
operating temperature.Oil viscosity is expressed in either SUS (Saybolt Universal
Seconds) or in cSt (centistokes). Centistoke viscosity is an international standard
and is more widely used.

ASTM D-2270 determines the Viscosity Index (VI) of an oil. It is an empirical
number used to measure an oil’s ability to resist viscosity changes when the tem-
perature changes. High VI oils have smaller viscosity changes than low VI oils
when the temperature changes. Viscosity Index cannot be used to measure any
other quality of an oil.

ASTM D-943 is used by AGMA to evaluate the oxidation stability of R&O gear
oils. This test measures an oil’s ability to resist oxidation in a wet environment
by heating an oil / water mixture to 203ºF and recording the number of hours it
takes for the oil / water mixture to reach an acid number of 2.0. Although AGMA
uses this test for gear oils, it can test the oxidation stability of steam turbine oils
or any oil subjected to water contamination.

ASTM D-2893 is a “dry air oxidation test” for EP gear oils only. The test nor-
mally is run for 13 days at 203ºF. To make the test more severe, AGMA increased
the test temperature to 250ºF. A test temperature of 250ºF instead of 203ºF is
more severe because the rate of oil oxidation doubles with every 18ºF increase
in temperature. A gear oil that is oxidation stable in this 250ºF test will be more
oxidation stable at the relatively low gear box temperatures of 140ºF to 180ºF.
Gear oils that are oxidation stable reduce the frequency of oil changes, resulting
in significant dollar savings to the user. The advanced oxidation stability of
Royal Purple’s oil can increase oil drain intervals up to 15,000 hours. This is six
times longer than AGMA’s recommended 2,500 hours oil change interval.

ASTM D-665 rust test is used by AGMA to determine a gear oil’s ability to pro-
tect ferrous metals from rust in both fresh and saltwater environments.

ASTM D-130 is normally run at 212ºF, but to make the test more severe AGMA
increased the temperature to 250ºF. ASTM D-130 is used to determine the cor-
rosiveness of a gear oil’s EP additive to nonferrous metals. A polished copper
strip is immersed in the 250ºF oil bath for three hours and the EP additive corro-
siveness is determined by comparing the strip against ASTM pre-rated strips.
ASTM rates the test strip as: 1 a or b; 2 a, b, c, d or e; 3 a or b; or 4 a, b, c or d.
Ratings of 1 a or 1 b are the least corrosive.

Interpretation of AGMA Test Results

AGMA Performance Requirements
for R&O, Worm, EP and Synthetic gear oils

3

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