The degree to which two greases, usually with different thickeners, can meet in a bearing without harm. Incompatible mixes typically soften and run out of the housing, and occasionally harden, both leading to failure. Compatibility is tested by blending in set ratios such as 50/50 and 10/90 and checking dropping point, penetration and shear stability under ASTM D6185. Polyurea with lithium and clay with most soaps are the classic clashes.
We're switching suppliers, so check grease compatibility before anybody pumps new product into everything.
Never trust a compatibility chart alone: two greases with the same thickener can still fight if their base oils or additive packages clash.
Also heard as
- grease mixing
- compatibility
Related terms
Soup
Grease that has broken down or been mixed with an incompatible type and turned runny.
Polyurea
Non-soap grease thickener with long high-temperature life, standard in sealed electric motor bearings.
Thickener
Solid structure in a grease, usually a metal soap or polyurea, that holds the base oil like a sponge.
Purge
To pump fresh grease into a bearing until the old grease is pushed out of the relief port or seal.