Mobilgrease 28

Synthetic Aviation Grease

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 high viscosity index compared to mineral oils, provide excellent low temperature pumpability, very low starting and running torque, and can help 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 excellent 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 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 Methods	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 40ºC	30
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
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) Typical properties are typical of those obtained with normal production tolerance and may vary slightly, while remaining within specified limits.

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