And now boys and girls the long awaited second chapter of Oil and Grease. Yes, you guessed it; it?s the grease part.
Greases are thickened oils that seal, protect, cushion and provide long service life. The types of oil (synthetic or mineral) and the type of thickeners (Calcium, Lithium, Bentonite, and Molybdenum Disulfide also know as Moly) are blended together to meet the specific demand of the application. Calcium (Lime) thickened oils have a high water resistance but a poor high temperature performance. Lithium based greases have a high melting points and adequate water resistance. Inorganic gels do not melt and the grease does not soften at high temperatures
Greases are categorized by their usage. A low-speed, high-pressure gear requires a different grease characteristic than high-speed roller bearing grease. High-pressure sliding surfaces require extreme pressure additives such as Molybdenum Disulfide. Low or moderate pressure sliding surfaces may require grease that will not evaporate, prevent water wash off and prevent corrosion. Roller bearings require ?clean? grease that has significant thermal stability.
Grease, because of its thick nature tends to attract and hold contaminants. These contaminants (dirt and sand) will tend to damage the very thing that the grease is there to protect. To reduce the amount of contaminants, it is necessary to thoroughly clean the area to be lubricated, prior to application. My maintenance manual likes Stoddard?s solvent and M.E.K. your mileage may very. Of course only lay out the new grease after the solvents are gone. To add insult to injury, it is not a good practice to mix synthetic oil greases with mineral oil grease, because they are not compatible.
| Mil Spec | Shell | Royal Manufacturing Company | Oil Type | Notes |
| MIL-G-3545C (obsolete) | Aero Shell 5 | Royal 45 | Mineral | high temperature aircraft wheel bearing and engine accessory grease. It is made with high viscosity base oil and a Microgel? non-melting inorganic thickener, providing excellent load carrying ability and resistance to water washout. |
| MIL-G-24139A MIL-G-7711a (obsolete) |
Aero Shell 6 | Royal 11 | Mineral | general-purpose airframe grease used primarily in plain and anti-friction bearings. It is made with a Microgel inorganic thickener, which provides outstanding low temperature torque properties and resistance to water. |
| MIL-PRF-23827C | Aero Shell 7 | Royal 27 | Synthetic | low temperature multipurpose aviation grease recommended for instruments and general airframe lubrication of turbine powered aircraft as well as highly loaded gears and actuator screw mechanisms |
| MIL-G25537C | Aero Shell 14 | Mineral | multipurpose helicopter grease used for most helicopter main and tail rotor bearings (where specified). It is made with mineral base oil and a calcium soap thickener which provides outstanding protection against moisture, corrosion & fretting. | |
| MIL-G25760A (obsolete) | Aero Shell 16 | Royal 25 | Synthetic | Synthetic inorganic gel grease with moderate water resistance but superior oxidation and corrosion resistance. |
| MIL-G-21164D | Aero Shell 17 | Royal 64 | Synthetic | extreme pressure multipurpose grease recommended for heavily loaded sliding steel surfaces where protection against seizure and corrosion is desired; e.g. bogie pivot pins on jet aircraft landing gear assemblies. |
| MIL-PRF-81322F | Aero Shell 22 | Royal 22 | Synthetic | Wide tempature performance makes this a preferred grease in jet aircraft. Also this is the only approved grease for all Cleveland Wheels |
| MIL-PRF-23827C | Aero Shell 33 | Synthetic | AeroShell Grease 33 has esablished itself as the answer to most general purpose, airframe greasing requirements, setting the standard with exceptional anti-corrosion and anti-wear performance while allowing you to shrink your grease inventory and reduce the risk of misapplication | |
| MIL-G-21164D | Aero Shell 33SM | Synthetic | This is a new Grease on the marked. Marked as a direct replacement for Aero Shell 17 |