Can You Mix Greases?

Mixing incompatible greases can soften them until they run out of the bearing. Here is how to switch safely.

Step 1Check both thickeners
Find the thickener on each data sheet (lithium complex, polyurea, calcium sulfonate, clay and so on). The thickener decides compatibility more than the base oil.
Step 2Assume “not compatible” until proven
Published charts disagree on many pairs. If the pair is not clearly compatible, treat it as incompatible.
Step 3Purge, do not top up
When switching, pump new grease through until clean new grease comes out of the relief or seals, then shorten the next relube interval to flush out remaining old grease.
Step 4Test when it matters
For critical equipment, ask for a compatibility test per ASTM D6185, which checks the mixture for dropping point, consistency and shear stability.

General notes by thickener

Polyurea: Often incompatible with soap greases such as lithium and calcium. HUSKEY MP-2 is polyurea; purge fully when switching.
Clay (bentonite): Usually borderline or incompatible with soap greases.
Calcium sulfonate: Has broad compatibility, but is often listed as borderline with calcium complex, clay and conventional polyurea.
Lithium and lithium complex: Usually compatible with each other; often borderline with polyurea and clay.

General guidance only. Compatibility depends on the exact products; confirm with the manufacturers or ASTM D6185 testing.

Tell us about your application and we’ll recommend the right product.