Short answer
Polyurea grease uses a non-soap organic thickener made by reacting isocyanates with amines, so it contains no metal soap. Polyurea greases are known for oxidation resistance and long service life, which makes them common in electric motor bearings and other sealed-for-life or hard-to-reach applications. Compatibility with other thickeners varies, so mixing should be checked first.
A non-soap thickener
Most greases are thickened with metal soaps such as lithium, calcium or aluminum soaps. Polyurea is different: the thickener is an organic polymer-like compound with no metallic component, sometimes described as ashless. Without metal soap, there is less to catalyze oxidation of the base oil at high temperatures, which supports long life in bearings that run warm for years.
Why motor bearings often use it
Electric motor bearings tend to run at moderate to high speeds and steady temperatures, are often lubricated for long intervals or for life, and generally do not need extreme-pressure additives. Some EP chemistries are considered undesirable near motor windings. Polyurea greases formulated for motors fit that profile, and polyurea is a common factory fill in motor bearings.
Polyurea greases are also used in constant-velocity joints, sealed wheel bearings and some steel mill applications, in formulations designed for those duties.
Compatibility and shear
Compatibility between polyurea and other thickeners depends on the specific products; published studies have found some polyurea and lithium complex blends tested acceptably, but that is not a general rule. When a motor was filled with polyurea, keep using the same type unless the motor maker approves a change, and purge old grease when switching.
Some polyurea greases can soften or harden with shear or storage. Shear-stable polyurea formulations exist, and data sheets may report prolonged worked penetration or roll stability to show how a product behaves.
Before you relubricate a motor
Check the motor nameplate or manual for grease type and quantity. Over-greasing is a common cause of motor bearing problems, because excess grease churns and heats or can be pushed into the windings. Follow the manufacturer’s amount, interval and relief-plug procedure.
Frequently asked questions
Can I use polyurea grease in place of lithium complex?
Only after checking compatibility and the equipment maker’s recommendation. Purge the old grease when changing thickener types.
Is polyurea grease good in water?
Water resistance depends on the full formulation, not just the thickener. Check water washout or spray-off data on the product sheet.
General maintenance information. Always follow your vehicle or equipment manufacturer’s requirements and the current product data. Questions? Email [email protected].