How to Select the Right Industrial Bearing Grease: Key Parameters for Optimal Performance

Key Parameters for Optimal Performance

When it comes to industrial bearing maintenance, choosing the right grease is not just a maintenance task—it’s a critical investment in the longevity and reliability of your machinery.

For bearing factory, bearing manufacturing company, and bearing OEM operations, the stakes are even higher, as suboptimal lubrication can lead to costly downtime, premature failures, and compromised product quality.

At JRZC, we’ve spent decades refining our approach to bearing lubrication, and we’re sharing our key insights to help you make informed decisions.

Grease is a combination of solid or semi-solid thickeners added to mineral oil or synthetic lubricating oil. Grease is like a "sponge" filled with lubricating oil; the fibers in the "sponge" are the thickeners, and the base oil and additives in the "sponge," like lubricating oil, perform the lubrication function.

1. NLGI Consistency Grade

The Foundation of Grease Selection

The consistency, or “hardness,” of a grease, measured by the NLGI (National Lubricating Grease Institute) grade, is the first parameter to consider. It dictates how the grease behaves under shear, its ability to stay in place, and its flow characteristics.

NLGI Classification Table

For most rolling bearings, the sweet spot is NLGI 2.

This grade, often described as having the consistency of peanut butter, offers an ideal balance:

• Excellent sealing properties

• Strong leakage resistance

• Broad application compatibility

For high-vibration or high-temperature environments, or for vertically mounted bearings where gravity is a factor, NLGI 3 is preferred to prevent the grease from being thrown out.

Conversely, for low-temperature applications or centralized lubrication systems, NLGI 1 or even semi-fluid grades (00–0) are more suitable.

2. Thickener Type

The “Sponge” That Holds the Oil

The thickener, which makes up about 15% of the grease, is the “sponge” that holds the base oil and releases it under shear.

It’s a primary determinant of:

• Mechanical stability

• Drop point

• Operating temperature range

For high-speed applications or long-life requirements, mechanical stability is paramount.

Greases like:

• Complex lithium-based greases

• Polyurea-based greases

are excellent choices. These thickeners maintain their structure under repeated shear, preventing the grease from softening and being expelled from the bearing.

The thickener also dictates the grease’s temperature capabilities.

For example:

• Standard lithium-based greases have a drop point around 190°C

• Long-term recommended use is around 140°C

For higher temperatures, specialized options like fluorinated greases become necessary.

3. Base Oil and Viscosity

The True Lubricant

Comprising 70–95% of the grease, the base oil is the component that actually provides lubrication.

Its viscosity is the key to forming a robust oil film between bearing components.

A common misconception is that “faster speeds need harder grease.”

In reality:

Faster speeds require lower viscosity base oils to minimize internal friction and heat generation.

ISO VG Selection Table

Selection Guidelines

• High-speed, light-load applications
  (e.g., electric spindles, precision textile machinery)
  → ISO VG 32, 46, 68

• Low-speed, heavy-load applications
  (e.g., mining crushers, heavy rolling mills)
  → ISO VG 220, 320, 460

• General-purpose applications
  (e.g., standard motors, fans)
  → ISO VG 100

4. Extreme Pressure (EP) Performance

Handling Heavy Loads

Under heavy or shock loads, the oil film can be compromised, leading to mixed or boundary lubrication.

This is where EP performance becomes critical.

The weld load, measured in Newtons, is a key indicator of a grease’s ability to withstand extreme pressure.

Load Classification Table

C: Basic dynamic load rating (kN)
P: Equivalent dynamic bearing load (kN)

Practical Weld Load Reference

• Light to medium loads
  (e.g., motor bearings) → ~2000 N

• Heavy or shock loads
  (e.g., mining machinery) → ≥3000 N

• Extreme loads
  (e.g., continuous casting machines) → ≥4000 N

Look for “EP” in the grease name or a gray/black color, which often indicates the presence of solid additives.

However, use these greases sparingly, as solid additives can be abrasive and cause damage if not strictly necessary.

5. Operating Temperature and Drop Point

Many people mistakenly believe that if a grease has a dropping point of 200 ℃, it can be used continuously at 200 ℃. This is completely wrong.

The dropping point only indicates the temperature at which grease changes from a semi-solid paste to a liquid—it is a physical transition point, not a performance safety limit.

A reliable rule of thumb: maximum continuous operating temperature ≈ dropping point − 50 ℃. In other words, the safe long-term use temperature of most greases is roughly 50 ℃ below their dropping point. The exact value depends on the grease’s consistency, thickener type and concentration, and the base oil viscosity.

If the grease is used at or above its dropping point, it will melt and flow away. Therefore, the dropping point should only be used as a reference when initially selecting grease for temperature conditions.

For example, ordinary lithium-based grease has a dropping point of about 190 ℃. Its long-term safe operating temperature is therefore around 140 ℃. Exceeding this temperature accelerates oil oxidation, causes the grease to dry and carbonize, and ultimately turns it into “asphalt,” which can seize bearings.

High-Temperature Grease Example

Grease life is also heavily temperature-dependent.

For every 10–15°C rise above 70°C, the grease’s service life is halved.

For sustained high-temperature operation (>150°C), consider high-performance options like fluorinated greases, which excel in extreme heat and chemical environments.

About JRZC: Your Trusted Partner in Industrial Bearing Solutions

JRZC brings 22 years of specialized expertise to the global industrial bearing market. We are committed to stable, high-quality products, professional technical support, and comprehensive R&D, design, and OEM/ODM services, serving customers in more than 20 countries worldwide. At JRZC, we understand there is no “one-size-fits-all” solution for bearing lubrication; the optimal grease choice is a precise function of operating speed, load, temperature, and environmental conditions. By systematically evaluating these critical parameters, we empower bearing factory and bearing OEM operations to transform lubrication from a reactive cost center into a proactive driver of reliability, efficiency, and long-term profitability.