Mobilgrease™ 28

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Aircraft component in a factory

Mobilgrease™ 28 grease — the first synthetic product Mobil offered — has been trusted for more than 50 years.

Mobilgrease 28 is a Polyalphaolefin (PAO), clay-based multi-purpose airframe and wheel bearing grease of choice for many aircraft operators around the world. Designed to lubricate 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.

It meets the performance requirements of key military and commercial aviation specifications and offers operators increased flexibility and potential inventory consolidation benefits.  Mobilgrease 28 is fully approved for use in multi-purpose airframe grease applications and in wheel bearings.

Common grease point applications

  • Gears, actuators, jack screws
  • Helicopter rotor bearings
  • General airframe (splines, slats, stabilizers, elevators)
  • Landing gear assemblies
  • Flight controls
  • Aircraft wheel bearings 

Reasons to trust in Mobilgrease 28

  1. It offers operators outstanding anti-wear protection to help extend aircraft component life
  2. Mobilgrease 28 delivers exceptional protection against rust and corrosion in equipment
  3. Provides optimal load and weight bearing performance, even under extreme heavy load applications 
  4. Resists deterioration in extreme temperatures and helps keep equipment operating at peak performance 
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Product information

   Mobilgrease™ 28 performance profile 335.303 KB/pdf
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  • Boeing
  • Airbus
  • Maximize component life
  • Resists degradation
  • Extended temperature range
  • High temperature stability
  • Water resistance
  • Wear protection
  • Load carrying capabilities
  • Friction control
  • Military use
  • Anti-wear grease
  • Wax-free
  • High viscosity
  • Wheel bearing grease
  • Multi-purpose airframe grease
  • MIL-PRF-81322G
  • DOD-G-24508A, Amendment 4
  • NATO G-395

Resources

Aviation lubricant shelf life

Find out the recommended shelf life of ExxonMobil aviation lubricants.

English, Technical topics

Grease compatibility and conversion guidance

Learn what grease compatibility is, and how it impacts grease conversion and performance.

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Understanding oil bleed and grease separation

Learn what causes oil bleed and grease separation, how to identify what is normal and what is excessive, and how to minimize separation.

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Storage and handling recommendations and best practices

Applying the first-in, first-out (FIFO) inventory method can help reduce the risks of oil and grease deterioration caused by lengthy storage. Learn more.

English, Technical topics

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 synthetic hydrocarbon 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 helps 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
Advantages and potential benefits
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 helps extend bearing life and reduce 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

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 is also 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 qualified by the U.S. Military under Specification MIL-PRF-81322, General-Purpose, Aircraft, and 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
Is Approved Against
Quality Level
MIL-PRF-81322G X

DOD-G-24508A, Amendment 4

X
NATO G-395 X

Typical properties

Test Method
Mobilgrease 28 Typicals (1)
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 307 (584) 232 (450) min
Viscosity of Base Oil, cSt ASTM D 445

at 100ºC

5.7

Low Temp. Torque at -54ºC (-65ºF), Nm (g-cm) ASTM D 1478

Starting

0.43(4400) 0.98 (10,000) max
Running, after 1 Hr

0.05 (510) 0.098 (1,000) max
Penetration @ 25ºC (77ºF), 60 Stoke Worked, mm/10 ASTM D 217 293 265-320
Extended Worked Penetration Stability, 100,000 Strokes, mm/10 FTM 313 303 350 max
Oil Separation, 30 Hrs at 177ºC, wt % ASTM D 6184 3.5 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 1b 1b max
Four-Ball Wear, Scar dia, mm ASTM D 2266 0.6 0.8 max
Load Wear Index, kgf ASTM D 2596 40 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 (modified) 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
Dirt Count, Particles/mL FTM 3005

25-74 Micron

Pass 1000 max
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) Typical properties are typical of those obtained with normal production tolerance and may vary slightly, while remaining within specified limits.


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