How to Grease Your Electric Motor Bearings

May 10, 2023

Bearing failure is one of the top causes of motor failure and it's important to grease your bearings regularlly. We’ve recorded a video showing you the step-by-step guide to grease your bearings, or read the below article for the step by step guide.

In this article, we’re covering:

How Often to Grease Motor Bearings

Since maintaining your bearings by greasing them is so important, how often should it be done? The manufacturer of the motor and the manufacturer of the bearing will have a specific recommended greasing schedule. The intervals between greasing will be specific to the motor load, run time, and ambient temperature.

Common intervals are every month, quarter, or year. Make sure you understand how your electric motor is running and where, so you keep an optimal greasing schedule. As mentioned, the manufacturers may also specify how much grease to use. However, the amount of grease also depends on how often the motor runs, what environment it will be in, and the bearing size.

If your motor’s running all day every day, you’re going to want to grease it more frequently, vs a motor that only runs a few times a week. Also, a motor in a dusty environment like an aggregate site will need to be greased more than a motor in a clean manufacturing facility. Over-greasing can cause just as many issues as under-greasing. Too little grease leads to higher friction and heat, causing the lubrication to break down and the bearings to wear prematurely.

Too much grease leads to internal bearing pressure that also causes higher friction and heat. This can also damage seals causing the grease to migrate into the motor windings and allowing space for contamination to enter the bearing. The grease gun you use will need to be calibrated by how many grams each shot is to deliver the exact amount of grease needed.

How to Grease Motor Bearings

Now that we know how often to grease our bearings, we can walk through the step-by-step process.

  1. Step one: The motor should be running and warm.
  2. Step two: Remove any covers to get to the greasing locations. There are usually two grease zerks on an electric motor, one on the drive end and one on the non-drive end. The grease fittings are often at the top or slightly to the side of the motor.
  3. Step three: Remove any grease zerk caps and the purge valve cover. The caps help keep contaminants off the grease zerks for easy cleaning and the purge valve allows grease to escape in case there is a pressure build-up.
  4. Step four: Clean the grease fittings and the grease gun to avoid adding contaminants to the grease. Dispense one shot of grease from the gun to ensure it is clean and working properly.
  5. Step five: Apply grease gun to the grease fitting and dispense the recommended amount. If you see grease coming out of the purge valve, stop adding any more grease to avoid overfilling issues.
  6. Step six: Clean the grease fittings and any grease around the workstation.
  7. Step seven: Replace the purge valve cover, any grease zerk caps, and any other components you have removed. Now we’re done greasing the motor.

Why Do Motors Need Grease

Understanding the purpose of the lubricant in your electric motor bearings will help you see the importance of regular preventative maintenance, ensuring your motor performs well for a long time. The purpose of lubricants in general is to support sliding loads. Lubricant or grease helps to reduce friction and wear, seal against contaminants, disperse heat, and prohibit rust and corrosion. Plus, when elements run smoother, the amount of energy needed to do the work is reduced, helping you to save on energy costs.

Best Grease for Electric Motor Bearings

There are many types of lubricants that can be used with electric motors and selecting the correct one is important. Greases are made up of viscous oil that is either mineral or synthetic-based and has been mixed with a thickening agent. The most common types of grease used for electric motors have a base oil viscosity of one hundred centistokes and a thickening complex made of polyurea or lithium.

We typically see manufacturers using polyrex EM by Mobil. You should consult the motor’s manual to confirm the recommended amount of grease suggested by the manufacturer. You can find your motor on a product page.

First, find your product by typing in your catalogue number found on the motor nameplate. Once on the product page, click ‘downloads’ and you’ll see the manual, data package, feature sheet, and warranty policy.

Can’t find your motor? Contact our team at and our team of specialists will help you find the right grease for your motor.

You should also keep note of your load and operating temperature when selecting the lubrication grade. Make sure you don’t mix different types of grease. Mixing grease types, manufacturers, weights, and additives will lead to the same issues as other types of contamination. The grease will have a short life, as will the bearings.

How to Store Bearing Grease

How you store your electric motor lubricants is just as important as selecting the correct viscosity and grade. You don’t want to contaminate your grease before it even gets into the bearing to do its job. Store your grease in a clean, dry, and temperature-controlled area. If the grease gets too hot or too cold, it can break down in the holding container.

Your grease gun should only be used with one specific type of grease to avoid cross-contamination and stored in a clean, dry, and temperature-controlled area as well.

How Do You Know When Your Bearings Need More Grease

There’s newer technology that helps keep precise track of how often you need to grease your motor and how much. Ultrasound or sonic technology allows you to monitor your grease levels and quality with precision.

The ultrasound technology allows you to perform maintenance based on conditions rather than based on the calendar, which helps you to avoid over- or under-greasing situations more easily. This technology “listens” to the bearings to monitor the friction level. When grease is needed, it is slowly introduced into the system until the ideal sound is detected.

However, an estimation will suffice for most applications and it’s most important to have a consistent greasing schedule.

Do All Motors Need Grease

There are some motors that have sealed, permanently greased bearings. These bearings are meant to last as long or longer than your motor with minimal maintenance. In this case, your motor won’t require greasing as a regular maintenance practice. You will need to still check the health of the bearings on occasion as contamination can still occur. If caught early, the bearings can be replaced, and the motor can still run effectively and efficiently for a long time. This typically applies to motors under 30 horsepower.

How to Check Your Bearings

Issues with bearing lubrication often lead to bearing failure. If you're hearing more noise coming from your motor or the running temperature has increased, it may be worth checking and potentially replacing your bearings.

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