dnewton3
Staff member
All -
This is being posted as a sticky for reference. Often questions arise about greases which can be easily answered in this article. One of the most important things to realize is that there are a lot of greases which are not compatible with others. Whereas many oils which meet API specs can be safely mixed within their category (SN, GL-5, etc), that same context does not always exist with grease. Performance specs for grease do not assure compatibility; greases which meet the same performance standard can have vastly different make-up and not work well together. And to further add concern, some grease compatibility charts actually contradict other charts!
https://www.machinerylubrication.com/Read/30727/determine-grease-compatibility
" Several contradictions were discovered among the various charts. ... Although there were significant disagreements between the various charts, they all had one thing in common - few provided any link or reference to research that was conducted to develop them. That is to say, the charts being used to make significant engineering and design decisions are contradictory and do not indicate the source of information or research used to compile them."
https://www.machinerylubrication.com/Read/1865/grease-compatibility
"To add to the confusion, there are some grease specifications that are based solely on grease performance without regard to grease composition. If greases of different thickener types (both of which meet the performance requirements of the specification) get mixed in service, dire consequences can result."
If i understand correctly; for example your axle calling for GC/LB (refers to applications) and NLGI#2 (refers to thickness), it does not mean that all greases meeting those specs are compatible.
If you are unsure of what grease currently exists in your application, you have two choices:
1) completely purge the application and use a grease you choose which will have the correct performance criteria for that application
2) contact the maker of the component and ask if they can give you the specific brand name and product number of what was installed OEM, assuming it has not been altered by someone else prior to your ownership
In low-load/low-speed applications, this may not matter much (ex: hinge pins, low-frequency sliding contact, etc).
In high-load/high-speed applications it matters quite a bit (ex: wheel bearings, pulley bearings, loaded shaft bearings, high-pressure contact surfaces, etc).
This is being posted as a sticky for reference. Often questions arise about greases which can be easily answered in this article. One of the most important things to realize is that there are a lot of greases which are not compatible with others. Whereas many oils which meet API specs can be safely mixed within their category (SN, GL-5, etc), that same context does not always exist with grease. Performance specs for grease do not assure compatibility; greases which meet the same performance standard can have vastly different make-up and not work well together. And to further add concern, some grease compatibility charts actually contradict other charts!
https://www.machinerylubrication.com/Read/30727/determine-grease-compatibility
" Several contradictions were discovered among the various charts. ... Although there were significant disagreements between the various charts, they all had one thing in common - few provided any link or reference to research that was conducted to develop them. That is to say, the charts being used to make significant engineering and design decisions are contradictory and do not indicate the source of information or research used to compile them."
https://www.machinerylubrication.com/Read/1865/grease-compatibility
"To add to the confusion, there are some grease specifications that are based solely on grease performance without regard to grease composition. If greases of different thickener types (both of which meet the performance requirements of the specification) get mixed in service, dire consequences can result."
If i understand correctly; for example your axle calling for GC/LB (refers to applications) and NLGI#2 (refers to thickness), it does not mean that all greases meeting those specs are compatible.
If you are unsure of what grease currently exists in your application, you have two choices:
1) completely purge the application and use a grease you choose which will have the correct performance criteria for that application
2) contact the maker of the component and ask if they can give you the specific brand name and product number of what was installed OEM, assuming it has not been altered by someone else prior to your ownership
In low-load/low-speed applications, this may not matter much (ex: hinge pins, low-frequency sliding contact, etc).
In high-load/high-speed applications it matters quite a bit (ex: wheel bearings, pulley bearings, loaded shaft bearings, high-pressure contact surfaces, etc).
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