Mobil Grease 28: Superior Synthetic Grease for High-Load Aircraft Systems

This article is part of Greenwood Aerospace’s ongoing series on ExxonMobil aviation lubricants. Designed to assist procurement professionals, maintenance crews, and fleet managers, the series provides insights into the right lubricant products for specific mission profiles. 

Be sure to check out our other articles on Mobil Grease 33 All-Temperature Aircraft Grease and Mobil AGL Gear Lubricant Synthetic Helicopter Gear Oil to gain a comprehensive understanding of ExxonMobil’s aviation grease and gear oil offerings.

A Look at Synthetic Grease

Mobil Grease 28 synthetic aircraft grease is a purpose-built grease for high-speed applications and superior load-carrying capacity. Wherever severe operating conditions exist, your fleet is exposed to extremes. Mobil Grease 28 is a high-temperature synthetic grease made from a polyalphaolefin (PAO) synthetic base fluid combined with an organo-clay thickener, delivering superior lubrication. This is especially useful for plain and rolling bearings, although it is not made for wheel bearings. 

Note: For wheel bearing, you will need Mobil Grease 33, which you can find here: 

Key Features Benefits

With a high drop point of approximately 307°C, Mobil Grease 28 remains stable in demanding applications, far more than older petroleum-based greases, which tend to fail under similar conditions

In addition to handling high heat, this grease resists being washed out by water and continues to perform reliably in loads that would wash out older greases in short order. Its formula is also designed to prevent excessive wear and tear, helping protect the life of critical parts in aircraft systems for a long time. 

Mobil Grease 28 Specifications & Approvals

With synthetic hydrocarbon base oils and MIL-PRF-81322G compliance, Mobil Grease 28 is an excellent multipurpose grease featuring a proprietary additive combination that provides long grease retention and high water resistance. Here are the specs:

  • NATO Code G-395
  • MIL-PRF-81322G (US Military General Purpose Aircraft Grease)
  • MIL-PRF-24508B (Navy shipboard auxiliary machinery)
  • Meets or exceeds DIN 51825:2004-06 KP 1 N -20 and KP 2 N -20 standards
  • Compliant with NLGI HPM+WR for water resistance and high performance
  • NLGI Grade: 1.5; Dark red, smooth buttery texture 

Performance in High-Temperature Conditions

Mobil Grease 28 has a high dropping point of 307 °C, so it remains stable and continues to operate under high-temperature conditions. It resists high-temperature stresses and gives outstanding performance in all situations, making it suitable for everything from primary trainers like the T-6 Texan II and the T-1 Jayhawk to tactical aircraft in the AOR. 

This grease offers excellent high-temperature stability, reducing maintenance and replacement costs, and a quality level backed by the ExxonMobil name. 

Comparison to Other Products

Mobil Grease 28 performs exceptionally well against other greases in severe operating conditions, particularly in environments with high bearing loads and speeds. However, we also stock and recommend AeroShell grease as a suitable substitute. 

Mobil Grease 28 is a wax-free composition that provides excellent low-temperature pumpability and high-temperature performance. It is formulated with synthetic base oils that provide it with superior load-carrying ability and help prevent excessive wear, unlike mineral oils, which are typically used. With a load wear index of 40 kgf, 0.6 mm wear scar, and minimal corrosion, it provides superior friction reduction and wear protection for modern aircraft systems. 

Mobil Grease 28 provides reliable lubrication and reduces frictional drag in heavy-duty sliding mechanisms and control systems.

Properties and Characteristics of Mobil Grease 28

Ideal to reduce operating temperatures in plain and roller bearings, and also suitable for hinges. With a wax-free nature, Mobil Grease 28 checks a lot of boxes. Here are the operating properties and characteristics: 

  • Base Oil Viscosity: 29.3 mm²/s @ 40ºC; 5.7 mm²/s @ 100ºC
  • Dropping Point: 307ºC
  • Load Wear Index: 40 kgf
  • Four-Ball Wear Scar: 0.6 mm
  • Low Temperature Torque: 0.43 Nm (starting), 0.05 Nm (running) at -54ºC
  • Water Washout: 1% mass loss @ 41ºC
  • Passes oxidation stability and rust tests; smooth, buttery texture

Health and Safety

As with other industrial lubricants, health and safety information can be found in the Material Safety Data Sheet (MSDS). It is formulated for safe handling and low volatility in aviation and industrial environments, making it a safe option. 

Keeping Your Fleet Running Smoothly

From electric motors to accessory drive systems and even static joints, your fleet of machinery needs the best grease that money can buy. And it does more than just that:

  • Engine accessories
  • Servo mechanisms
  • Airframe lubrication
  • Landing gears
  • Hinge pins
  • Screw jacks
  • Running torque tubes
  • Worm gears
  • And more!

All of these aircraft sections are ideal candidates for Mobil Grease 28. But remember, it is not made for aircraft wheel bearings; for that, you need Mobil Grease 33. 

The Greenwood Aerospace Advantage: Your Trusted Partner in Government Procurement

Greenwood Aerospace is proud to serve you from right here in the heartland. Located in Ponca City, Oklahoma, we are strategically located near the Aviation Capital of the U.S. and have partnered with the biggest names in the business to support your federal or military fleet. 

We are also a Native American-owned, HUBZone-certified small business, and we can help you with your procurement needs. You can source the products directly through our links to GSA Advantage listings, or you can contact us at gsasales@greenwood.aero or 833-GSA-EBUY (833-472-3289). If you need bulk or expedited shipping, we can arrange that for you, too. 

Additional Resources

This guide is part of Greenwood Aerospace’s comprehensive ExxonMobil lubrication series. Each article in the series is designed to help aviation maintenance and procurement teams make informed purchasing decisions by using verified GSA Advantage listings. 

For additional resources, explore our related posts on Mobil Grease 28, Mobil Grease 33, and Mobil AGL Gear Lubricant, or contact Greenwood Aerospace directly for assistance with GSA orders or bulk pricing.

We also recommend that your read the main article in this series for a broad overview of the ExxonMobil line of greases: The Greenwood Aerospace Guide to ExxonMobil Aviation Greases and Gear Lubricants.