ISOFLEX TOPAS NB 52 vs Mobil Polyrex EM: Bearing Grease Comparison
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Is Polyrex EM a direct substitute for NB 52?
The manufacturer data reviewed for this article does not confirm a direct substitution. ISOFLEX TOPAS NB 52 uses a barium complex thickener; Mobil Polyrex EM uses polyurea and is marketed for electric-motor bearings. Check the equipment’s lubricant specification before choosing between them.
What the manufacturer data establishes
| Check | ISOFLEX TOPAS NB 52 | Mobil Polyrex EM |
|---|---|---|
| Manufacturer description | Rolling and plain bearing grease | Electric-motor bearing grease |
| Thickener | Barium complex | Polyurea |
| Base oil | Synthetic hydrocarbon | Published base-oil viscosity: 115 mm²/s at 40 °C and 12.2 mm²/s at 100 °C |
| Temperature information | Klüber’s public page states −50 to +120 °C. Short peaks to +150 °C depend on the application. | Mobil lists a 260 °C dropping point and a laboratory bearing-life test at 177 °C. Neither value by itself defines an approved operating range. |
| Speed limit | No numeric limit verified in the public product page used here | No numeric limit listed in the product table used here |
Swipe the table sideways to read every column.
Manufacturer data checked on 29 September 2026: Klüber: ISOFLEX TOPAS NB 52; Mobil: Polyrex EM product data.
The entries above have different purposes. A viscosity value, a dropping point and a bearing-life test cannot be compared as though they were interchangeable ratings. Use the current regional product data sheets to fill any missing fields before making a technical selection.
Read temperature figures with their conditions
Klüber’s short-duration temperature statement for NB 52 depends on the application. It should not be turned into a continuous spindle-bearing rating. For Polyrex EM, the temperature printed beside a test identifies that test condition. It does not establish a maintenance interval for your motor.
SKF’s maintenance handbook distinguishes a grease’s dropping point from its operating temperature limit. For a replacement decision, record steady temperature, peaks and their duration, and ask for the product’s service limits for the relevant duty.
Source: SKF: bearing maintenance handbook, page 185.
Polyrex EM and EM 103 have different consistency grades
Mobil lists Polyrex EM as NLGI 2 and Polyrex EM 103 as NLGI 3. Copy the full name into a purchase request. A quote for “Polyrex” leaves the grade unresolved, even when the supplier understands the intended bearing application.
Source: Mobil: Polyrex EM product data.
How to make a replacement decision
- Find the approved lubricant in the equipment or bearing documentation. If it names NB 52, keep that requirement attached to the enquiry.
- Collect the bearing designation, speed, measured temperature and relubrication arrangement. Note any seal materials or process fluids identified by the manufacturer.
- Request the missing product data and a written suitability assessment for the proposed alternative.
- Agree the changeover method, fill quantity and restart checks before maintenance begins.
For a spindle, include the assembly designation and the maker’s running-in procedure. For a motor, identify the drive-end and non-drive-end bearing arrangements where they differ. Those details let the reviewer assess the actual lubrication points.
Questions before ordering
Can I top up NB 52 with Polyrex EM?
The sources used here do not confirm compatibility of that exact mixture. Obtain advice for the two products and follow an approved changeover procedure.
Which grease has the higher speed limit?
No supported numerical ranking is available from the public product pages cited here. Request the current product information and compare limits using the same bearing and speed-factor definition.
Check the NB 52 pack before ordering
The linked listing is for a 370 g cartridge. Include your required quantity and the exact lubricant specification in the enquiry.
Sources and product data
Manufacturer and NSF pages checked on 29 September 2026. Confirm the current product documents for the supplied grade and region.
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