Polyurea describes a grease thickener family, not a universal approval for every bearing. Choose a lubricant by the exact equipment requirements, operating conditions and documented compatibility with what is already present. This page concerns electric-motor bearing grease, the subject of Yenra’s original Polyrex EM article; it is not about spray-on protective coatings.
Start with the equipment, not the cartridge
Record the motor make, model, serial number, bearing designation where documented, mounting orientation and operating duty. Find the lubrication nameplate and the correct manual revision. Establish whether the bearing is intended to be relubricated at all. A sealed-for-life assembly and a serviceable bearing do not imply the same maintenance task.
As an example of why instructions matter, Baldor’s MN409 motor manual, lubrication section (PDF) gives precedence to the motor’s lubrication nameplate and directs users to seek approval and instructions when changing from the specified lubricant. It concerns the motors covered by that manual; its quantities and intervals must not be copied to an unrelated motor.
Read several properties together
Mobil’s electric-motor grease selection explanation distinguishes oil viscosity from grease consistency. Record values with their test temperature and units. A higher number is not automatically better; the question is whether it meets the application’s requirement.
Scroll horizontally on a narrow screen. Keyboard users can focus the table region and use the arrow keys.
| Field | What it describes | What to verify |
|---|---|---|
| Thickener | The structure that holds the lubricating oil | Exact product chemistry and compatibility evidence, not just a family label. |
| Base oil and viscosity | The lubricating fluid and resistance to flow at a stated temperature | Oil type and viscosity appropriate to the documented duty. |
| NLGI grade | Grease consistency or firmness | The grade specified for this bearing arrangement. |
| Temperature information | A stated operating recommendation or a particular laboratory test | Do not treat a dropping-point result as an approved continuous operating limit. |
| Approvals and applications | Manufacturer claims with a defined scope | Whether the exact equipment and proposed use are covered. |
Save the current regional product data sheet and safety data sheet together. The first helps identify properties and applications; the second addresses hazards and handling. Neither by itself replaces the equipment maker’s service procedure.
Similar product names can hide different grades
The Mobil Polyrex EM product data lists Polyrex EM as NLGI 2 and Polyrex EM 103 as NLGI 3. It describes EM 103 for applications where the OEM may require a stiffer consistency, including certain vertical or very large motors. Both use polyurea thickener, yet that shared label does not make them automatic substitutes.
Resolve mixing and changeover as separate questions
Mobil reports compatibility testing for particular products and directs specific inquiries to its representative. That is narrower than saying all greases with the same thickener are compatible. Ask about the exact old and new products, the application and the proposed changeover. Record who answered, when, and under what conditions.
If the existing grease is unknown, state that explicitly. Color, texture and an old unlabeled grease gun are inadequate product records. Have the equipment maker or responsible lubrication specialist define the next step. Do not turn a general compatibility chart into an improvised purge, cleaning or relubrication procedure.
Create a controlled selection record
Keep one record per application: required product or specification, approved alternatives, source documents, confirmation of compatibility, and the authorized procedure reference. Include storage and identification arrangements so the selected product reaches the intended point without confusion. Mark obsolete labels and instructions through your organization’s maintenance process.
Have qualified personnel perform maintenance under the machine’s isolation and service requirements. This selection guide intentionally supplies no generic amount, interval or number of grease-gun strokes. The finished result is a traceable product decision and an applicable work instruction, not merely a cartridge whose label sounds appropriate.
Save a working record
Download the working record (plain text). Open it in a text editor and save a private copy. Fill in the prompts, write “unknown” where evidence is missing, and attach the documents behind each conclusion. It includes this article’s address and source links.