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For most industrial electric motors with regreasable rolling bearings, the best general-purpose choice is a high-quality electric-motor-bearing grease that is polyurea-thickened, NLGI grade 2, with base-oil viscosity around 100–160 cSt at 40°C, and strong oxidation resistance. In practice, Mobil Polyrex EM is one of the most widely specified examples, and ABB documentation lists it as the standard grease provided with anti-friction-bearing motors in some product lines. Comparable purpose-built products also include SKF LGHP 2 and Black Pearl Grease SRI 2 (formerly Chevron SRI Grease). (library.e.abb.com)
The important correction is this: there is no single universal “best” grease for every motor. The true best grease is the one specified by the motor or bearing OEM, because shaft orientation, speed, bearing type, temperature, and whether the existing grease is polyurea or lithium-based all matter. (library.e.abb.com)
When people ask about grease for electric motors, they are almost always talking about bearing grease, not the motor internals generally. For that application, official manufacturer guidance converges on a fairly consistent profile: good electric-motor grease should have suitable base-oil viscosity for speed/load, NLGI consistency appropriate to the bearing arrangement, high oxidation resistance, good shear stability, and a high dropping point. Mobil’s bearing-lubrication guide says NLGI 2 is the most commonly used grade in electric motor service, while ABB’s current motor manual says re-greasing grease should typically use lithium complex or polyurea thickener, 100–160 cSt base-oil viscosity at 40°C, and NLGI 1.5 to 3, with grade 2 or 3 recommended for vertical or hot-mounted machines. (mobil.com)
Polyurea grease is so commonly recommended for electric motors because it is specifically favored in motor-bearing applications for long grease life, oxidation resistance, mechanical stability, and high-temperature performance. Mobil states that a polyurea thickener is increasingly used in electric motor bearings, and its Polyrex EM line is recommended by many major bearing and electric-motor manufacturers. SKF similarly positions LGHP 2, a polyurea (di-urea) grease, as suitable for small, medium, and large electric motors, including high-speed fans and vertical shaft applications. (mobil.com)
That is why, if you want the shortest practical answer, it is: use a polyurea electric-motor-bearing grease unless the nameplate/manual says otherwise. For many users in North America, Mobil Polyrex EM is the safest “default” answer because it is both widely used and explicitly called out by ABB/Baldor documentation. (library.e.abb.com)
Polyurea is not mandatory in every case. ABB’s manual explicitly accepts either lithium complex soap or polyurea, provided the viscosity and consistency are correct, and it lists several approved lithium-based alternatives alongside Polyrex EM. So if your motor OEM specifies a lithium-complex product, that may be entirely correct for that machine. (library.e.abb.com)
This matters because many failures blamed on “bad grease” are actually caused by using the wrong thickener family, mixing incompatible greases, or overgreasing, not by choosing a bad brand. Mobil warns that greases with different thickener types should generally be considered incompatible unless compatibility testing proves otherwise, and ABB says plainly: do not mix greases. (mobil.com)
For most horizontal-shaft motors, NLGI 2 is the normal selection. If the motor is vertical-shaft, very large, or runs hotter, a stiffer grease may be preferred. Mobil notes that Mobil Polyrex EM 103 is specifically recommended for vertically mounted bearings or very large motors where a stiffer consistency may be required, while ABB recommends NLGI 2 or 3 for vertically or hot-mounted machines. (mobil.com)
A common mistake is focusing only on “polyurea vs lithium” and ignoring base-oil viscosity. ABB’s current guidance specifies 100–160 cSt at 40°C, and SKF LGHP 2 is in that range at 96 cSt at 40°C, which is consistent with a medium-speed electric motor bearing grease. Too heavy a base oil increases churning and heat; too light a base oil can reduce film strength. (library.e.abb.com)
Mobil’s guide says it is generally advisable to use grease without EP additives unless the motor bearing is carrying a thrust load that actually requires them; otherwise EP additives can shorten grease life. ABB likewise notes that lubricants containing EP admixtures are not recommended for general use in these motors. (mobil.com)
From a maintenance standpoint, these are the main practical hazards:
If the motor has double-shielded or double-sealed bearings, the correct answer may be no grease at all, because those bearings are often lubricated for life. Mobil states that such bearings usually do not require regreasing and come prepacked with the correct amount of grease from the factory. (mobil.com)
Current OEM and lubricant-manufacturer information still strongly supports purpose-built electric-motor greases, especially polyurea-based products, rather than generic multipurpose grease. ABB’s recent manuals continue to list Mobil Polyrex EM as the standard grease for anti-friction-bearing motors and also list Chevron SRI #2 and several lithium alternatives. SKF’s current LGHP 2 data sheet continues to position a polyurea motor grease as suitable for electric motors, high-speed fans, and vertical shafts. (library.e.abb.com)
A notable product trend is the availability of synthetic polyurea electric-motor greases for more demanding duty. Mobil’s SHC Polyrex 100 EM series is marketed for longer relubrication intervals, high-temperature protection, and even measurable reduction in bearing torque versus a mineral-oil comparison grease. That does not make it necessary for every motor, but it shows where premium motor-lubrication products are going. (mobil.com)
For VFD-driven motors, grease selection alone is not enough if bearing-current damage is the real issue. ABB’s current guidance emphasizes shaft grounding devices to divert induced shaft voltages and prevent EDM/fluting in inverter-duty service. (new.abb.com)
| Motor/application | Best practical grease choice |
|---|---|
| Standard industrial motor, horizontal shaft | Polyurea, NLGI 2, ~100–160 cSt @ 40°C |
| Vertical shaft motor or hotter installation | Polyurea or OEM-approved grease, often NLGI 2–3 |
| Very high temperature / long relube interval | Synthetic motor grease, usually polyurea-based |
| Existing motor with known lithium-complex grease | Stay with OEM-approved lithium-complex unless fully cleaned and changed |
| Sealed-for-life bearings | Do not regrease unless OEM explicitly instructs it |
This table is a synthesis of current ABB, Mobil, and SKF guidance. (library.e.abb.com)
From a safety and compliance standpoint, the main issue is not ethics in the abstract; it is asset reliability, worker safety, and correct chemical handling. Use the OEM-approved lubricant, follow the product PDS/SDS, and do not improvise with a grease whose compatibility or application rating is unknown. In regulated environments such as food, pharma, or hazardous areas, you should also confirm that the grease carries the required approvals for that site, not just that it is “good for motors.” (mobil.com)
If your motor runs with bearing temperatures above about 100°C, ABB advises consulting the manufacturer for a suitable grease rather than assuming the standard product is still appropriate. (library.e.abb.com)
Also, if this is a small appliance motor, a fractional-horsepower motor, or a sealed bearing motor, the answer can be completely different from a regreasable industrial NEMA motor. (mobil.com)
If you want the truly best grease for your exact motor, gather these four items:
With that information, selection becomes an engineering decision rather than a generic recommendation. OEM documentation plus the grease PDS is the right next step. (library.e.abb.com)
For a general answer, the best grease for electric motors is usually a polyurea electric-motor-bearing grease, NLGI 2, with about 100–160 cSt base-oil viscosity at 40°C, and Mobil Polyrex EM is one of the strongest default recommendations. However, the best actual choice is always the grease specified by the motor OEM, and the biggest reliability rules are: do not mix greases, do not overgrease, and do not regrease sealed-for-life bearings. (library.e.abb.com)
If you want, I can narrow this to your specific motor if you give me the motor brand, RPM, bearing type, and whether it is horizontal, vertical, or VFD-driven.