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Synthetic Aerospace Oils & Greases
Mobilgrease 28 is a supreme performance, wide-temperature, antiwear grease
designed to combine the unique features of a polyalphaolefin (PAO) synthetic
base fluid with an organo-clay (non-soap) thickener. Its consistency is
between an NLGI No. 1 and No. 2 grease. It offers outstanding performance over
a wide temperature range. The wax-free nature of the synthetic base fluid,
together with its low coefficient of traction compared with mineral oils,
provide excellent low temperature pumpability, very low starting and running
torque, and can reduce operating temperatures in the load zone of rolling
element bearings.
The clay thickener gives Mobilgrease 28 a
high dropping point value of around 300ºC, which provides excellent stability
at high temperatures. Mobilgrease 28 resists water washing, provides superior
load-carrying ability, reduces frictional drag, and prevents excessive wear.
Tests show that Mobilgrease 28 lubricates effectively rolling element bearings
under conditions of high speeds and temperatures. Mobilgrease 28 has also
shown superior ability to lubricate heavily loaded sliding mechanisms, such as
wing flap screw jacks.
For more than 30 years, Mobilgrease 28
has been the multi-purpose grease of choice for military and related aviation
applications, worldwide.
Features and Benefits
A particular requirement of aviation greases is the need to resist high
temperature stresses, while providing excellent starting and low torque at
low-temperature. To meet this combination of needs ExxonMobil product
formulation scientists chose proprietary synthetic base oils for Mobilgrease
28 because of their low volatility, exceptional thermal/oxidative resistance,
and superb low-temperature capability. Formulators chose specific thickener
chemistry and a proprietary additive combination which would maximize the
benefits of the synthetic base oils.
Mobilgrease 28 meets the
requirements of key military and commercial aviation specifications and has
built up a superb reputation for performance and reliability among users
around the world.
Mobilgrease 28 provides the following advantages and potential benefits:
Features
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Advantages and Potential Benefits
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High viscosity index (VI) synthetic base stock with no wax content
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Allows wide operating temperature range - outstanding high and low temperature
performance
Provides thicker fluid films protecting against wear of
equipment parts operating at high temperature
Causes low resistance
during start-up at very low temperatures
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Excellent protection against wear and corrosion
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Superb bearing protection and extended bearing life and reduced bearing
replacement costs
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Extreme-pressure protection characteristics
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Avoids excessive wear, even under shock load
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High thermal/oxidative stability
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Long relubrication intervals
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High resistance to water washout
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Maintains excellent grease performance in adverse weather and other
water-exposure conditions
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Applications
Mobilgrease 28 is designed for the lubrication of plain and rolling bearings
at low to high speeds, and splines, screws, worm gears, and other mechanisms
where high friction reduction, low wear, and low lubricant friction losses are
required. The recommended operating temperature range is -54ºC to 177ºC (-65ºF
to 350ºF) with appropriate relubrication intervals.
Mobilgrease 28 is recommended for use in landing wheel assemblies, control
systems and actuators, screw jacks, servo devices, sealed-bearing motors,
oscillating bearings, and helicopter rotor bearings on military and civil
aircraft. Subject to equipment manufacturer approvals, it can also be used on
naval shipboard auxiliary machinery and where superseded specifications
MIL-G-81322 (WP), MIL-G-7711A, MIL-G-3545B, and MIL-G-25760A are recommended.
Mobilgrease 28 also is recommended for industrial lubrication, including
sealed or repackable ball and roller bearings wherever extreme temperature
conditions, high speeds, or water washing resistance are factors. Typical
industrial applications include conveyor bearings, small alternator bearings
operating at temperatures near 177ºC (350ºF), high-speed miniature ball
bearings, and bearing applications where oscillatory motion, and vibration
create problems.
Mobilgrease 28 is of quality level U.S.
Military Specification MIL-PRF-81322, General-Purpose, Aircraft, and U.S.
Military Specification DOD-G-24508A (Navy) for shipboard auxiliary machinery.
It is a U.S. Military Symbol WTR and NATO Code Number G-395 grease.
Specifications and Approvals
Mobilgrease 28
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Is Approved Against
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Quality Level
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| MIL-PRF-81322 | X | |
| DOD-G-24508A | | X |
| Nato G-395 | X | |
Typical Properties
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Test Methods
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Mobilgrease 28 (1)
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MIL-PRF-81322 Limits
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| >NLGI Grade | | 1 1/2 | |
| Thickener Type | | Clay (non-soap) | |
| Color | Visual | Dark Red | |
| Structure | Visual | Smooth, buttery | |
| Dropping Point, ºC (ºF) | ASTM D 2265 | 315 (599) | 232 (450) min |
| Viscosity of Base Oil, cSt | ASTM D 445 | | |
| at 40ºC | | 29.3 | |
| at 100ºC | | 5.6 | |
| Low Temp. Torque at -54ºC (-65ºF), Nm (g-cm) | ASTM D 1478 | | |
| Starting | | 0.83 (8500) | 0.98 (10,000) max |
| Running, after 1 Hr | | 0.08 (800) | 0.098 (1,000) max |
| Penetration @ 25ºC (77ºF), 60 Stoke Worked, mm/10 | ASTM D 217 | 295 | 265-320 |
| Extended Worked Penetration Stability, 100,000 Strokes, mm/10 | FTM 313 | 302 | 350 max |
| Oil Separation, 30 Hrs at 177ºC, wt % | ASTM D 6184 | 2.5 | 2.0 - 8.0 |
| Evaporation Loss, 22 Hrs at 177ºC, wt % | ASTM D 2595 | 6 | 10 max |
| Copper Strip Corrosion, 24 Hrs at 100ºC | ASTM D 4048 | Pass | 1b max |
| Four-Ball Wear, Scar dia, mm | ASTM D 2266 | 0.5 | 0.8 max |
| Load Wear Index, kgf | ASTM D 2596 | 42 | 30 min |
| Rust Protection, 48 Hrs at 125ºF, › 1mm dia Corrosion Spots | ASTM D 1743 | Pass | 0 |
| Water Washout, 1 Hr at 41ºC, wt % | ASTM D 1264 | 1 | 20 max |
| High Temperature Performance, Hrs at 177ºC | ASTM D 3336 | Pass | 400 min |
| Oxidation Stability, pressure drop in kPa | ASTM D 942 | | |
| 100 Hrs at 99ºC | | Pass | 83 max |
| 500 Hrs at 99ºC | | Pass | 172 max |
| Storage Stability, 6 months at 38ºC | FTM 3467 | Pass | Pass |
| Dirt Count, Particles/mL | FTM 3005 | | |
| 25-74 Micron | | Pass | 1000 max |
| 75 Micron or Larger | | 0 | 0 |
| Oscillation Friction and Wear, Scar Dia, 35,000 cycles, 90º Angle, Aluminum Bronze Block, mm | Modified ASTM D 3704 | Pass | 6.35 max |
| Rubber Swell, L Type Synthetic, 1 week at 70ºC (158ºF), vol % | FTM 3603 | 6 | 10 max |
| (1) Values may vary within modest ranges | | | |
Health and Safety
Based on available toxicological information, this product is not expected to
produce adverse effects on health when used and handled properly. Information
on use and handling, as well as health and safety information, can be found in
the Material Safety Data Sheet (MSDS) which can be obtained from your local
distributor or via the Internet on http://www.exxonmobil.com/lubes.
PDS AV-05
The ExxonMobil logotype and Mobilgrease are trademarks of Exxon Mobil Corporation, or one of its subsidiaries.
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