Short answer
NLGI consistency has 9 grades (000, 00, 0, 1, 2, 3, 4, 5, 6). Higher number = harder. Grades 1 and 2 cover most applications.
What is NLGI consistency?
Grease "softness" is called consistency, measured by penetration (depth in 0.1mm a 60° cone sinks in 5 seconds):
- Higher penetration → softer grease → flows more easily
- Lower penetration → harder grease → flows less
The 9 grades
| Grade | Penetration range | Flow behavior | Typical use |
|---|---|---|---|
| 000 | 445–475 | Like honey | Centralized lubrication |
| 00 | 400–430 | Thin honey | Centralized lubrication |
| 0 | 355–385 | Like yogurt | Heavy gears |
| 1 | 310–340 | Like peanut butter | General bearings (medium load) |
| 2 | 265–295 | Like butter | Most common — general bearings |
| 3 | 220–250 | Hard butter | High-speed bearings |
| 4 | 175–205 | Harder | Heavy-load low-speed |
| 5 | 130–160 | Very hard | Special |
| 6 | 85–115 | Soap-like | Almost no flow |
Grades 1 and 2 cover ~80% of applications.
How to choose
Principle: speed first, load second, grease method last
| Application | Recommended |
|---|---|
| High speed (>3000 rpm) | 1 or 2 |
| Medium (1000–3000) | 2 |
| Low speed (<1000) | 2 or 3 |
| Heavy low-speed | 3 or 4 |
| Centralized lubrication (long pipes) | 0 or 1 |
Soft vs hard in practice
Soft grease (grade 1):
- Flows well, low starting resistance;
- Easy to sling and leak;
- More oil separation.
Hard grease (3–4):
- Stays put, good sealing;
- Higher starting resistance;
- Hard to deliver to remote lubrication points → risk of starvation.
Conclusion
Neither too soft nor too hard. Most bearings do well with grade 2. Adjust ±1 grade based on conditions.
Related reading
- 《NLGI Grade Selection》— choose consistency by application scenario;
- 《How Much Grease Should You Add?》— consistency affects fill quantity limits.