Mixing the wrong greases is one of the fastest ways to turn routine maintenance into a costly repair. Even if both greases perform well individually, their chemical makeups might clash—resulting in separation, hardening, or total lubrication failure.
This guide helps you understand grease compatibility, why it matters, and how to avoid mixing incompatible greases using industry-standard charts.
What Is Grease Compatibility?
Grease compatibility refers to how well two different greases blend together.
Incompatible greases can chemically react and:
- Separate (oil weeps out, thickener clumps)
- Harden into a dry, waxy mess
- Turn to liquid and run out of bearings
- Lose anti-wear and extreme pressure properties
Why Incompatibility Happens
Grease has three main components:
- Base oil
- Thickener
- Additives
Even if base oils are the same, the thickener types can conflict. For example, lithium and polyurea greases often don’t mix well.
The Grease Compatibility Chart
| Thickener A/B Complex | Lithium Complex | Polyurea | Calcium Sulfonate | Aluminum Complex |
| Lithium Complex | ✅ Compatible | ⚠️ Borderline | ⚠️ Borderline | ❌ Incompatible |
| Polyurea | ⚠️ Borderline | ✅ Compatible | ❌ Incompatible | ❌ Incompatible |
| Calcium Sulfonate | ⚠️ Borderline | ❌ Incompatible | ✅ Compatible | ⚠️ Borderline |
| Aluminum Complex | ❌ Incompatible | ❌ Incompatible | ⚠️ Borderline | ✅ Compatible |
✅ = Compatible, ⚠️ = Use caution (testing needed), ❌ = Incompatible
Pro Tip: When switching grease types, fully purge the system or flush bearings before applying new product.
Common Mistakes That Lead to Incompatibility
- Topping off with whatever’s nearby
- Bulk tanks or manual pumps not labeled
- Switching to “premium” grease without checking chemistry
- Using contractor grease alongside OEM product
How to Avoid Grease Compatibility Issues
- Stick with one brand/type across your equipment if possible
- Label grease guns and pumps clearly by type
- Purge and clean before changing grease types
- Consult OEMs or suppliers for safe substitutions
- Use a compatibility chart as a reference
Internal Links
Ready to switch greases? First, learn how to choose the right one →
Working in extreme heat? Check out our High-Temp Grease Guide →
