Every grease tin carries an NLGI number. It is the single most quoted grease property, and also one of the most misunderstood. The number tells you how firm the grease is. It does not tell you how good it is, how hot it can run or how much load it can carry.
NLGI grades describe grease consistency, from 000 (almost fluid) to 6 (a hard block). NLGI 2 suits most rolling bearings. NLGI 3 suits larger bearings, vertical shafts and some hot or vibrating positions. NLGI 0, 00 and 000 are used in centralised lubrication systems and some enclosed gear units. Base oil, thickener and additives decide the rest.
The NLGI scale comes from the National Lubricating Grease Institute. Grease is first worked 60 strokes in a standard grease worker at 25 °C. Then a standard cone is dropped into it, and the depth it sinks in five seconds is the worked penetration, measured in tenths of a millimetre (ASTM D217). Softer grease lets the cone sink deeper, which means a higher penetration and a lower NLGI number.
| NLGI grade | Worked penetration | Feels like | Typical uses |
|---|---|---|---|
| 000 | 445–475 | Fluid | Some enclosed gear units, centralised systems |
| 00 | 400–430 | Semi-fluid | Enclosed gearboxes, centralised systems, cold conditions |
| 0 | 355–385 | Very soft | Centralised systems, long lines |
| 1 | 310–340 | Soft | Centralised systems, low temperatures, some bearings |
| 2 | 265–295 | Like peanut butter | Most rolling bearings, general purpose |
| 3 | 220–250 | Firm | Large bearings, vertical shafts, wheel bearings, vibration |
| 4 | 175–205 | Very firm | Special applications |
| 5–6 | 85–160 | Hard to block | Special applications such as block greases |
NLGI 2 is soft enough to reach the rolling elements and flow back into the contact zone, yet firm enough to stay in the bearing housing and seal against dirt. It also pumps easily from a grease gun. That balance makes it right for most electric motors, pumps, fans and conveyor bearings.
| Property | Why it matters | Where to find it |
|---|---|---|
| Base oil viscosity | Film strength. Slow, heavy bearings need thicker base oil | Data sheet, cSt at 40 °C |
| Thickener type | Temperature, water resistance, compatibility | Lithium, lithium complex, calcium sulphonate, polyurea |
| Dropping point | Upper temperature indication | Data sheet, °C |
| EP and anti-wear | Load and shock capacity | Four-ball or Timken test results |
| Water resistance | Wet and washdown areas | Water washout test |
That is why two NLGI 2 greases can perform very differently. For heat, see our high-temperature grease guide. For load, see EP2 vs MP3 grease.
In a 45 °C summer, grease in hot bearings softens. If grease keeps leaking out of seals in summer, the answer may be a different thickener or a grease with a higher base oil viscosity, not just a higher NLGI number. Do not mix greases when changing; read can you mix two different greases?
What does NLGI 2 mean?It is a consistency grade: worked penetration of 265–295 tenths of a millimetre. It is the most common grade for rolling bearings.
Is NLGI 3 better than NLGI 2?Not better, just firmer. NLGI 3 suits large bearings, vertical shafts and some vibrating applications. NLGI 2 flows into bearings more easily.
Which NLGI grade is used in centralised lubrication systems?Usually NLGI 0, 00 or 1, as stated by the system maker. Stiffer greases can block lines and metering valves.
Does a higher NLGI grade mean higher temperature resistance?No. Temperature performance depends mainly on the thickener and base oil. A firmer grade can soften less, but it does not raise the temperature limit by itself.
Tell us the equipment, speed, temperature and how it is greased (gun or centralised system), and our team will suggest the right grease and NLGI grade.