Grease Compatibility Chart

[GAHorn]

It is Never a good idea to Mix different types of greases because Some of them do not “play” well together.
Anyone who read my story about the time I was flying a U.S. vice-president for awhile will recall how an “emergency” was barely avoided when nose-wheel bearings failed on a rear-engine-mounted twin-jet due to a service-center using an incompatible grease. If those bearings had locked-up on Take-Off it might have thrown shredded tire rubber up and alongside the fuselage and into the engines…. I might have been even more InFamous than I am at present had that resulted in an accident.

Anytime grease is changed-out…it must be a suitable type (base-soap) ..and preferably the EXACT same as previously used…. OR the old grease MUST be COMPLETELY cleaned out and replaced entirely.

How do you know what specific type of grease you are seeing..? … either look at the fine print on the pkg…or inquire of the mfr’r.

OK… so… HERE is a CHART which… IF … BIG IF… you must swap grease…or you find you must add grease to an unknown type in-situ:

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PS: Most common greases are “Lithium Complex”….and most Synthetic Greases are “Polyurea”. Notice that even among synthetic greases …. they may not be “compatible” with each other.
Aeroshell 5 (commonly used for wheel bearings) and 6 both use a “Clay” thickener. Aeroshell 7 (commonly used for airframes) is a synthetic with water-resistant chemicals similar to “marine” greases (but should not be mixed with any other grease.) Aeroshell 22 is a synthetic often considered an “all around” grease, wheel bearings, engine accys, and airframe. Aeroshell 58 is lithium complex. Here is a link to other AeroShell greases: https://www.shell.com/business-customer ... eases.html#
Most “marine” greases (which I favor) are “Calcium Sulfonae” and are compatible with the second-favorite I use “Lithium Complex”. YMMV

[gfeher]

Recently an A&P/IA was doing an annual at my airport on a J3 in the process of being sold. He came from about 1-1/2 hr away, and it was the first time he came to my field. I noticed he had rack that he made holding about 8 or 9 grease guns each with a different grease in it. Various AeroShells and others. He said it was because his customers use different greases and he had one for each of the different greases. I had to give him credit and my respect. I wish he were closer. We have a shortage of good A&P/IA’s in my area. BTW, since there was no record of what grease was used on the J3, he cleaned and re-packed the bearings. Out of curiosity, I should have asked which grease he used.

[Bruce Fenstermacher]

BTW, since there was no record of what grease was used on the J3, he cleaned and re-packed the bearings.

Interesting, even with all the greases available, without documentation, how would one be certain. Since the bearings had to be inspected for the annual, and that is pretty tuff to do without cleaning them first, main bearings aren't a big deal. It is the grease zerk, previously wiped clean (as it should be) that is the devil.