Features Advantages and Potential 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.
- High viscosity index (VI) synthetic base stock with no wax content
- 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
- Excellent protection against wear and corrosion
- Superb bearing protection and extended bearing life and reduced bearing replacement costs
- Extreme-pressure protection characteristics
- Avoids excessive wear, even under shock load
- High thermal/oxidative stability
- Long relubrication intervals
- High resistance to water washout
- Maintains excellent grease performance in adverse weather and other water-exposure conditions
Application
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 -54?C to 177?C (-65?F to 350?F) 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 Subject to equipment manufacturer approvals, it can also be used on naval shipboard auxiliary machinery and where superseded specifications MIL-G-81322 (WP), MIL-G-7711A, MIL-G-3545B, and MIL-G-25760A are recommended.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 177?C (350?F), 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.
Typical Properties
|
Test Method |
Mobilgrease 28 |
MIL-PRF-81322 Limits |
| 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 |
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