NLGI Grease Grades Explained
When a grease is called “NLGI 2” or “#2 grease”, that number describes just one thing: how stiff it is. The National Lubricating Grease Institute grades consistency from 000 (almost fluid) to 6 (block-hard) using a single measured property — worked penetration. It says nothing about the thickener, the base oil or the performance; it only tells you the texture. Here is what each grade is, the numbers behind it, and how to choose one.
Consistency, and nothing else
Grease is base oil held in a thickener “sponge”. The NLGI grade rates how firm that sponge is — its consistency — and deliberately nothing else. Two greases can both be NLGI 2 yet be completely different products: one a lithium EP2, the other a polyurea — same stiffness, different chemistry, temperature range and life.
So the grade answers “will it pump, stay put and seal the way I need?” — not “how good is it?”. For performance you look at the thickener and additives; for texture you look at the NLGI number.
Counter-intuitive but important: a higher NLGI number means a harder grease. Softer greases penetrate deeper in the test, giving a higher penetration value but a lower grade number.
The NLGI consistency scale (ASTM D217)
Grade is set by worked penetration: a standard cone is dropped into grease that has been worked 60 strokes at 25 °C, and how far it sinks (in tenths of a millimetre, dmm) fixes the grade.
| NLGI grade | Worked penetration (dmm) | Texture | Typical use |
|---|---|---|---|
| 000 | 445–475 | Fluid (like syrup) | Gearboxes, centralised systems |
| 00 | 400–430 | Semi-fluid | Centralised lubrication, open gears |
| 0 | 355–385 | Very soft | Cold-climate, autolube systems |
| 1 | 310–340 | Soft | Low-temperature, high-speed bearings |
| 2 | 265–295 | “Buttery” — standard | General bearings, chassis, most uses |
| 3 | 220–250 | Firm | High-speed / vertical shafts, sealed bearings |
| 4–6 | 175–205 … 85–115 | Hard to block-hard | Grease blocks, plain bearings, special duty |
The scale steps in ~30 dmm bands. Each whole grade is a clearly different feel — a 00 flows, a 2 holds its shape like soft butter, a 4 must be cut with a knife.
How to pick a grade
Default to NLGI 2
For most rolling-element bearings, chassis points and general machinery, NLGI 2 is the standard — soft enough to pump and channel, firm enough to stay in the bearing and seal against contamination. When unsure, this is the safe choice.
Go softer (0/00/000)
For centralised/autolube systems that must pump grease down long lines, cold climates, or gearboxes running semi-fluid grease. Softer grades flow and pump far more easily but seal and stay-in-place less well.
Go firmer (3+)
For high-speed bearings, vertical or overhead shafts where a soft grease would slump out, and sealed-for-life units. A firmer grease resists throw-off and leakage but needs more pumping effort.
Match the equipment
Follow the OEM grease spec — it fixes both the NLGI grade and the performance class. We formulate to a target grade AND the thickener/EP/temperature performance the application needs.
NLGI grade vs the GC-LB performance mark
Do not confuse the consistency number with NLGI’s performance classification. For automotive grease, NLGI also certifies:
- GC — wheel-bearing grease performance (high-temperature life, corrosion, wear).
- LB — chassis grease performance (load, water resistance, wear).
- GC-LB — meets both, the top mark for automotive service; see our wheel-bearing grease.
So a premium automotive grease is described by two independent things: a consistency grade (usually NLGI 2) and a performance mark (GC-LB). The dropping point, base-oil viscosity and EP level round out the full picture.
Formulating to a target NLGI grade
Hitting a grade cleanly is a formulation and process skill — thickener yield, base-oil viscosity and cook process all move penetration. We build your grease to the target NLGI grade and the performance it needs — thickener chemistry, EP/AW and antioxidant package, dropping point and base-oil grade — then verify penetration, dropping point and EP in the lab. See the full grease formulation guide. The IP is yours.
Related guides
NLGI grade FAQ
What does NLGI 2 mean?
NLGI 2 is the standard grease consistency — a soft, buttery texture with a worked penetration of 265–295 tenths of a millimetre (ASTM D217). It pumps reasonably, stays in the bearing and seals well, which is why it is used for most rolling-element bearings, chassis points and general machinery.
Is a higher NLGI number harder or softer?
Harder. The NLGI scale runs from 000 (nearly fluid) to 6 (block-hard), so a higher number is a stiffer grease. A softer grease sinks the test cone deeper — a higher penetration value — but that corresponds to a lower NLGI grade number.
What is the difference between NLGI 00 and NLGI 2?
NLGI 00 is semi-fluid (penetration 400–430 dmm) and is used where grease must pump through long lines or run in a gearbox — centralised lubrication and open gears. NLGI 2 is much firmer (265–295 dmm) and stays in place in a bearing. They are chosen by how the grease must flow, not by quality.
Does the NLGI grade tell me the grease quality?
No. The NLGI number only rates consistency (stiffness). Quality and suitability come from the thickener type (lithium, complex, polyurea, calcium sulfonate), the base-oil viscosity, the dropping point and the additive package. Two NLGI 2 greases can perform very differently.
Which NLGI grade should I use?
For most applications, NLGI 2 is the default. Use a softer 0/00/000 grade for centralised/automatic lubrication systems, cold climates or gearboxes; use a firmer grade 3 for high-speed, vertical-shaft or sealed-for-life bearings that would throw off a soft grease. Always follow the equipment maker’s specification.
Need a grease at a specific NLGI grade?
From semi-fluid NLGI 00 for autolube systems to firm NLGI 3 for high-speed bearings — we formulate to the exact consistency and performance you need, then prove it in the lab. The IP is yours.
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