Aviation Greases explained

What makes aviation greases different from other lubrication grease types (e.g., bearing or multipurpose)?

Although aviation and other forms of lubricating greases may share some similar ingredients, aviation greases may differ in the technology and performance attributes required to meet or exceed the aviation industry specifications.

Aviation greases undergo very high levels of scrutiny regarding quality assurances and quality controls versus standard multipurpose greases. They also undergo extensive performance testing to assure compliance with OEM, military, and civil specification requirements. In addition, aviation grease formulations cannot substitute new additives, base oils, or thickeners without obtaining OEM, military, and civil authority endorsement. In many cases, full requalification of the grease may also be required before a change is approved.

What causes grease to produce an odor? Does grease odor impact performance?

While many base oils and additives used in greases have a defined odor when fresh, odors can also result from in-service degraded grease. Greases containing an ester base stock may be susceptible to hydrolysis and could generate an odor.

Some base stocks, such as polyalphaolefin (PAO), minimize odors when used in grease formulation.

For example, ExxonMobil aviation greases formulated from 100 percent polyalphaolefin

(PAO) base oil, such as Mobilgrease™ 33, will minimize these objectionable odors. Grease odor does not impact grease performance.

How do aviation greases help operators’ sustainability initiatives?

Grease with a long shelf life can reduce waste disposal, carrying costs, and inventory turnover, thereby advancing the sustainability initiatives of the operators.

It is imperative that such greases with long shelf life continue to offer the same quality of benefits throughout their entire lifespan.

A good example is Mobilgrease™ 33 and Mobilgrease™ 28, which offer a 10-year life span, and Mobil™ Aviation Grease SHC 100, which provides a 6-year life span.

What happens to greases when exposed to water?

We recommend avoiding exposure to high water concentrations, including precipitation and de-icing fluids on the tarmac. Potential issues could involve hardening or softening of the greases, increased corrosion, or decreased effectiveness of the performance additives. For greases formulated with ester base stocks, you may see increased hydrolysis or breakdown of the grease.

To be safe, we recommend that technicians evaluate their grease every 10,000 hours for irregularities and consult their supplier with any questions. Hydrolysis is preventable.

ExxonMobil Aviation greases are not formulated using ester base stock.

How long does grease last? What’s the average shelf life for aviation greases?

Shelf-life specifications can differ between aviation greases. The average industry shelf life of aviation greases is about three years. Some companies offer extended shelf life; for example, ExxonMobil aviation greases have extended shelf life ranging from six to 10 years – more than double the industry standard.

ExxonMobil aviation grease shelf life is listed as the “use by” date on the container. To maximize shelf life, normal storage temperatures should range from 0°C to 40°C (32°F to 104°F), and containers should be kept indoors in a clean and dry environment to avoid hydrolysis and other environmental factors.

What does the color of grease mean? Why does aviation have red, green, blue, and tan-colored greases?

The color of fresh grease is simply a function of dyes added to the formulation, which is often required by aviation industry organizations such as SAE International Aerospace or by an OEM QPL-specific directive. Specifications require other greases to be free of dyes. Different grease colors sometimes help to avoid accidentally mixing greases; however, greases with the same color are not always compatible. .

URCE | SHUTTERSTOCK PONGCHART B This article is courtesy of ExxonMobil Aviation. Find out more information via https://www.exxonmobil.com/en/aviation