Mobil Polyrex EM NLGI 2 Electric Motor Bearing Grease
Mobil Polyrex EM is an NLGI 2 polyurea grease formulated for electric motor ball and roller bearings. Its polyurea thickener system is designed to maintain consistency under mechanical shear while providing long-life lubrication in high-temperature bearing applications where low oil separation is important.
This blue electric motor bearing grease is also recommended for fin fan bearings, high-temperature pump bearings, factory-filled sealed-for-life ball bearings, and ball bearings used in noise-sensitive equipment. ExxonMobil states that Mobil Polyrex EM greases are recommended by many major bearing and electric motor manufacturers for long-life electric motor bearing lubrication.
Mobil Polyrex EM meets or exceeds the requirements of DIN 51825:2004-06, K 2 P -20.
Individual tube size: 13.7 oz. (388 g) per tube.
Key Benefits
- Designed for electric motor bearings: Formulated specifically for long-life lubrication of electric motor ball and roller bearings.
- High-temperature grease life: Provides a reported lubrication life of 750+ hours at 177°C in ASTM D3336 testing.
- Polyurea thickener: Designed for durability when exposed to mechanical shear forces.
- Low oil separation: ASTM D1742 oil separation of 0.5%, making it suitable for bearing applications where lubricant separation should be minimized.
- Rust and corrosion protection: Passes ASTM D1743 corrosion testing and provides additional protection under mild salt-water wash conditions.
- Low-noise performance: Suitable for ball bearings in many noise-sensitive applications.
- Water resistance: ASTM D1264 water washout of 1.9% at 79°C.
Recommended Applications
Mobil Polyrex EM is intended primarily for electric motor bearings, including ball and roller bearing designs. Other applications identified by ExxonMobil include:
- Electric motor bearings
- Fin fan bearings
- High-temperature pump bearings
- Factory-filled sealed-for-life ball bearings
- Ball or roller bearings operating at elevated temperatures where low oil separation is required
- Ball bearings used in noise-sensitive applications
Grease Compatibility
ExxonMobil reports that Mobil Polyrex EM greases have demonstrated compatibility with a number of ExxonMobil lithium complex greases and competitive mineral-oil polyurea electric motor greases using ASTM D6185 methodology.
This should not be interpreted as universal grease compatibility. Compatibility can vary by formulation, so confirm the existing grease and equipment manufacturer requirements before mixing products or changing grease types. For uncertain applications, consult the lubricant manufacturer or perform an appropriate compatibility evaluation.
Typical Properties
| Property |
Mobil Polyrex EM |
| NLGI Grade |
2 |
| Thickener Type |
Polyurea |
| Color |
Blue |
| Base Oil Viscosity @ 40°C, ASTM D445 |
115 mm²/s |
| Base Oil Viscosity @ 100°C, ASTM D445 |
12.2 mm²/s |
| Viscosity Index, ASTM D2270 |
95 |
| Worked Penetration, 60X, ASTM D217 |
285 |
| Penetration Change, 60X to 100,000X, ASTM D217 |
40 |
| Dropping Point, ASTM D2265 |
260°C |
| Lubrication Life @ 177°C, ASTM D3336 |
750+ hours |
| Oil Separation, ASTM D1742 |
0.5% |
| Four-Ball Wear Scar, ASTM D2266 |
0.48 mm |
| Low-Temperature Starting Torque @ -29°C, ASTM D1478 |
3,630 g-cm |
| Low-Temperature Running Torque @ -29°C, ASTM D1478 |
405 g-cm |
| SKF EMCOR Rust Test, 10% Synthetic Sea Water, ASTM D6138 |
0,1 |
| Corrosion Preventive Properties, ASTM D1743 |
Pass |
| Copper Strip Corrosion, ASTM D4048 |
1A |
| Water Washout @ 79°C, ASTM D1264 |
1.9% |
Note: Dropping point and ASTM D3336 test temperature are laboratory test values and should not be interpreted as the recommended maximum operating temperature of the grease.
Frequently Asked Questions
What type of grease is Mobil Polyrex EM?
Mobil Polyrex EM is a blue NLGI 2 polyurea grease formulated primarily for electric motor ball and roller bearings. Its base oil viscosity is 115 mm²/s at 40°C and 12.2 mm²/s at 100°C.
Is Mobil Polyrex EM designed for electric motor bearings?
Yes. Electric motor bearings are the primary application identified by ExxonMobil. The grease is also recommended for fin fan bearings, high-temperature pump bearings, sealed-for-life ball bearings, and other ball or roller bearings where low oil separation or low-noise performance is important.
What is the difference between Mobil Polyrex EM and Polyrex EM 103?
Mobil Polyrex EM is NLGI 2, while Mobil Polyrex EM 103 is the stiffer NLGI 3 version. ExxonMobil identifies Polyrex EM 103 for applications such as vertically mounted bearings or very large motors where the equipment manufacturer recommends a stiffer grease consistency.
Can Mobil Polyrex EM be used in sealed-for-life bearings?
ExxonMobil lists factory-filled, sealed-for-life ball bearings among the applications for Mobil Polyrex EM. Lubricant selection should still follow the bearing or equipment manufacturer's requirements.
Is Mobil Polyrex EM compatible with lithium complex grease?
ExxonMobil reports compatibility with a number of its lithium complex greases and certain competitive mineral-oil polyurea electric motor greases based on ASTM D6185 testing. This does not establish compatibility with every lithium complex or polyurea grease, so the specific products should be evaluated before mixing.
What is the dropping point of Mobil Polyrex EM?
Mobil Polyrex EM has a reported ASTM D2265 dropping point of 260°C. Dropping point is a laboratory property of the grease and should not be interpreted as its recommended maximum operating temperature.
Is Mobil Polyrex EM a high-temperature grease?
Mobil Polyrex EM is formulated for high-temperature ball and roller bearing lubrication. In ASTM D3336 testing, the PDS reports 750+ hours of lubrication life at 177°C. Actual grease life depends on bearing design, speed, load, operating temperature, contamination, relubrication practices, and other application conditions.
What grease is equivalent to Mobil Polyrex EM?
An alternative to Mobil Polyrex EM should be selected by comparing more than NLGI grade alone. Our PSC Grease Selector Tool can help identify products with similar specifications, but compatibility and suitability should be confirmed for the specific application. Thickener type, base oil viscosity, bearing speed, operating temperature, oil separation, corrosion resistance, and equipment manufacturer recommendations should all be considered.
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