NLGI Grades Explained: Grease Consistency Guide

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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