If you maintain industrial equipment, you know that what is nlgi grade? is one of those topics where getting it wrong costs real money — in downtime, in replacement bearings, in lost production. Here's what every maintenance engineer and reliability manager should understand about it.
TL;DR
- Understand what is nlgi grade? — and why it matters for equipment reliability
- Know the key differences in nlgi grade chart
- Apply the right faq for your operating conditions
What is NLGI Grade?
The National Lubricating Grease Institute (NLGI (National Lubricating Grease Institute, a standardized measure of grease consistency from 000 to 6)) grade is a standardized measure of grease consistency, ranging from 000 (very soft, fluid-like) to 6 (very firm, block-like). NLGI 2 is the most common grade for industrial bearing applications, offering a balance of pumpability and staying power.
NLGI Grade Chart
| NLGI |
Worked Penetration (0.1mm) |
Consistency |
Typical Application |
| 000 |
445-475 |
Very soft / fluid |
Enclosed gearboxes, centralized systems |
| 00 |
400-430 |
Semi-fluid |
Centralized lubrication, gearboxes |
| 0 |
355-385 |
Very soft |
Centralized systems, low-temp applications |
| 1 |
310-340 |
Soft |
Low-temperature bearings, high-speed applications |
| 2 |
265-295 |
Medium / buttery |
Standard industrial bearings (most common) |
| 3 |
220-250 |
Firm |
Large bearings, vertical shaft applications |
| 4-6 |
<205 |
Very firm / block |
Block grease, large open gears |
> Tip
A rule of thumb: for every 15°C increase above 70°C, grease life is cut in half. If your bearing housing is too hot to touch comfortably, check your lubrication — you may be over-greasing or using the wrong product.
FAQ
Q: How do I choose the right NLGI grade?
Selection depends on bearing size, speed, temperature, and application method. NLGI 2 is the default for most industrial bearings. NLGI 1 provides better low-temperature pumpability. NLGI 3 resists slumping in vertical shafts. Always consult your equipment manufacturer's specification.
Q: Can I use NLGI 1 instead of NLGI 2?
In many cases, yes — especially in cold environments where NLGI 1 offers better pumpability. However, NLGI 1 may leak from bearings designed for NLGI 2. The softer consistency provides less sealing capability but better flow at low temperatures.
Q: Why does grease consistency matter?
Consistency affects pumpability in centralized systems, retention in bearings, sealing against contaminants, and low-temperature starting torque. Too soft — grease leaks out. Too firm — grease doesn't reach the lubrication point.
Q: How is NLGI measured?
NLGI grade is determined by the worked penetration test (ASTM D217). A standard cone is dropped into a worked grease sample, and the penetration depth in tenths of a millimeter determines the NLGI number.
Q: How does temperature affect NLGI?
Grease softens as temperature increases and hardens as temperature decreases. A grease rated NLGI 2 at room temperature may behave like NLGI 1 at 80°C or NLGI 3 at -20°C. This is why temperature range is a critical selection factor.
KOEED Support
Need help selecting the right grease for your application? Contact KOEED at Moritta@KOEED.COM. Our technical team can provide KLÜBER product recommendations based on your operating conditions.
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