Not all lubricating greases can be interchanged. Supply chain issues and cost concerns are driving more industries to seek out alternative choices for lubricating greases. Lubrication technology is always changing making it even more important and more difficult to know that we are using compatible grease.
The Problem with Incompatible Grease
Combining incompatible greases can cause the oil to separate from the thickeners or cause the thickeners to harden. The first condition could result in oil run-out where the lubrication oil drips from the bearing leaving the bearing with no lubrication. The second situation could cause excessive friction and heating do to a thicker, higher viscosity lubricant.
The Industry Recommended Solution
The recommended solution is to purge as much grease from the system whenever we are changing the type or brand of grease being used. However, it is likely that some old grease will remain. Purging the old grease reduces the likelihood of problems arising but does not eliminate the problem completely.
We can reduce that chance even further by choosing compatible lubricating greases.
How do I Know Which Greases are Compatible?
Lubrication chemistry is complicated today and choosing the best replacement lubricant is difficult. ASTM International has developed standard ASTM D6185 - Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Grease. This is the standard manufacturers use to evaluate the compatibility of greases.
Most manufacturers provide their customers with compatibility charts and your suppliers representative should be able to help you with the selection process. An informed decision is best made when comparing specific brands and specific products from those brands.
A general compatibility chart can be found below. This chart does not consider specific brands or products but can serve as a starting point in determining compatibility.