Industrial MRO Reference Library · Wall Charts

Grease Compatibility Chart

General guidance on mixing greases with different thickeners, the pairings most often reported as a problem, and how to change over safely. Published charts disagree, so confirm with the grease makers.

Ref MRO-0085ASTM D6185

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Two greases are compatible if a mix of them keeps its consistency, heat resistance and shear stability. When incompatible greases mix, the blend can soften and run out of the bearing, or harden and stop flowing. Compatibility depends mostly on the thickener, but also on the base oil and additives. ASTM D6185 is the standard practice for testing a grease pair. There is no single official compatibility table. Charts from different grease makers do not always agree.

How to use it

Identify the thickener and base oil of the grease now in the equipment. Check the data sheet or the lube records.
Identify the same for the new grease.
Check both grease makers' compatibility statements. Treat any "borderline" or "unknown" result as incompatible.
If in doubt, purge the old grease fully before switching.

Commonly reported thickener pairings

Pairing	Commonly reported result
Lithium with lithium complex	Generally compatible
Lithium or lithium complex with calcium sulfonate complex	Often compatible; charts differ
Lithium or lithium complex with polyurea	Often incompatible or borderline
Lithium or lithium complex with aluminum complex	Often incompatible
Clay (bentonite, non-soap) with most soap thickeners	Often incompatible
Polyurea with polyurea from another maker	Varies; polyurea types differ
Same thickener, same base oil type, different maker	Usually compatible; additives can still conflict

Base oil notes

Base oil pairing	Typical guidance
Mineral with PAO synthetic	Usually compatible
Mineral with ester synthetic	Usually compatible; check seals
Mineral or PAO with silicone	Not compatible
Mineral or PAO with PFPE (fluorinated)	Not compatible; clean fully
Mineral with polyglycol (PAG)	Often not compatible

Key points

Mixing problems usually show up as softening, oil bleeding from the bearing or a sudden rise in temperature.
When changing over, purge with the new grease until clean new grease shows at the relief or seal. Then shorten the next interval or two.
Label grease guns and fittings with the grease used. One shared gun spreads the wrong grease.
Food-grade (H1) greases have their own thickener types. Check compatibility the same way.

Common mistakes

Assuming two greases are compatible because both are "NLGI 2."
Topping up with a different grease without purging.
Using one grease gun for several products.

Governing standards: ASTM D6185 (practice for evaluating grease compatibility); grease maker compatibility data; equipment maker lubrication requirements.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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