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NLGI 00 vs NLGI 2: When Soft Grease Is the Right Choice
NLGI grade is a consistency band, not a quality mark. NLGI 2 stays in a bearing. NLGI 00 moves down a long, cold line. The wrong grade starves an injector or greases the floor.
Direct answer
NLGI grade is consistency, not quality. NLGI 2 stays put in a wheel bearing or a hand-packed housing. NLGI 00 and NLGI 000 are soft enough to travel long lines and cold pipework. NLGI 2 in an unheated centralised system is how injectors starve. NLGI 00 in a hot, leaky housing is how the floor gets the grease instead of the bearing.
- ASTM D217 worked penetration at 25 °C is the measurement. The NLGI number is only the band that result falls in.
- Grade, thickener chemistry and base-oil viscosity are three knobs. Stiffer does not mean a stronger film.
- Centralised lines, cold starts, leaky housings and high-speed motors want different grades.
- Dual-stock NLGI 00 and NLGI 2 only inside one thickener family, in dedicated systems.
- Apparent viscosity and flow pressure tell you if the soft grease will still move in January.
ASTM D217 in one paragraph
ASTM D217, and the related ISO 2137, drop a cone into grease and report how far it sinks, in tenths of a millimetre, after the grease has been worked 60 strokes at 25 °C. NLGI built numbered grades on that scale. NLGI 000 is 445–475, NLGI 00 is 400–430, NLGI 0 is 355–385, NLGI 1 is 310–340, and NLGI 2 is 265–295. A higher grade number is a stiffer grease, meaning a lower penetration. It is not a higher-performance grease. Unworked penetration, 10,000-stroke or 100,000-stroke penetration, and roll stability by ASTM D1831 answer different questions: how the grease arrived, and whether shear in a line or a bearing will soften it out of grade.
Write the grade on the TDS only with the method and the temperature. “NLGI 2” with no D217 result is a label. A result measured at 40 °C in a warm lab and reported as if it were 25 °C is a different label. The grade guide on this site, NLGI grease grades, is the reference list. This article is the application choice that list cannot make for you.
Grade vs thickener vs base-oil viscosity — three different knobs
Plants turn one knob and hope the other two move with it. They do not. NLGI grade is mostly how much structure you built: thickener concentration, soap fibre or urea network, and how hard you milled it. Thickener chemistry is water resistance, heat and compatibility, which is why a calcium sulfonate NLGI 2 and a lithium NLGI 2 can share a number and not share a duty. Base-oil viscosity, measured by ASTM D445 and named as an ISO VG, is what largely sets film thickness on a slow, loaded surface.
So an NLGI 00 made on an ISO VG 460 oil can protect a slow pin better than an NLGI 2 made on an ISO VG 68 oil, and still flow in a dual-line system. The reverse mistake is also common in centralised plants: a buyer specifies NLGI 00, the blender complies by cutting thickener, and nobody checks that the oil left behind is still heavy enough for the pin. Ask for both numbers on the sheet. An NLGI 2 on a very light oil can look serious in the drum and still starve a slow bearing. Dropping point, ASTM D2265, is a fourth number people smuggle in as if it were grade. It is not. A soft polyurea and a stiff polyurea can share a drop-point class and need completely different pumps.
Centralised, cold-weather, leaky housing, high-speed motor
Centralised systems — single-line parallel, progressive dividers, dual-line — were built for greases that move. Long runs, small injectors and a cellar that sees a north-Indian winter will not reliably push NLGI 2. The grade the OEM names is the start. The check is pumpability: apparent viscosity by ASTM D1092, flow pressure by DIN 51805, and low-temperature penetration by ISO 13737. Some lubrication OEMs also publish a ventmeter limit. Use the one your hardware maker cites. Do not replace it with a finger test in April.
The opposite duties are just as common. A hot, worn housing with a tired seal will not hold NLGI 00; the grease leaves, the bearing runs dry, and the pit is clean only until the next cycle. Step up in grade, repair the seal, and do not “solve” leakage by thickening the grease with random soap on site. A high-speed electric-motor bearing usually wants a quiet, channeling NLGI 2, often a polyurea, not a soft extreme-pressure semi-fluid that slings and heats. Low-temperature torque methods, ASTM D1478 or ASTM D4693, belong to wheel bearings and similar cold starts, not to a kiln gear.
- Long cold line: softer grade, proved by D1092 or DIN 51805, not by adding oil to NLGI 2.
- Leaky hot housing: NLGI 2 or 3, and a seal.
- High-speed motor: NLGI 2 in the family the motor OEM allows.
- Slow loaded pin: look at the oil’s ISO VG before you look at the NLGI integer.
How plants dual-stock 00 and 2 without mixing them
Many plants do need both. The discipline is physical, not rhetorical. Same thickener family for both grades if a gun can ever meet a line. Dedicated pumps, dedicated fill couplers, and labels that state thickener, NLGI grade and ISO VG of the oil. Colour is a help only when it is controlled; two suppliers’ red greases are not a system. Never top an NLGI 2 bearing with the NLGI 00 drum because the 00 drum was closer to the job.
Storage is part of the spec. Softer greases show oil bleed sooner. ASTM D6184 on each grade tells you whether the drum is separating in your warehouse or whether the formula is too loose. A bled NLGI 00 that is stirred back with a stick is no longer the product you qualified. The industrial NLGI 2 path, if that is the manufactured SKU, is the EP2 grease formulation page. The NLGI 00 version is a different concentration and often a different oil, made under the same grease formulation engagement, not a diluted pail of the NLGI 2.
What Lubechem will and will not claim
Lubechem will not claim that NLGI 00 is “lighter duty” or that NLGI 2 is “heavy duty”. Those phrases confuse grade with film. We will not claim a centralised system we have tuned, or a percentage reduction in starved injectors. We formulate the grade you specify after the hardware, the ambient and the oil viscosity are written down.
Charts that say two NLGI grades of one family are “compatible” are still screens. They assume the thickener really matches. A lithium NLGI 00 and a polyurea NLGI 2 are not a dual-stock plan; they are a mixture. If the brief is a pair of grades for one plant, say so at the start so the bill of materials is two products, not one product and a wish.
NLGI bands that decide pump versus stay-put
| NLGI grade | ASTM D217 worked penetration, 0.1 mm | Typical hardware | Do not use it as |
|---|---|---|---|
| 00 | 400–430 | Long centralised lines, some gear-sump semi-fluids | A hot bearing with a worn seal |
| 0 | 355–385 | Shorter centralised lines, cold-weather feed | Proof that the oil is viscous enough |
| 1 | 310–340 | Centralised roll-neck and chassis systems | A substitute for fixing pumpability with solvent |
| 2 | 265–295 | Hand guns, motor bearings, most industrial housings | The default fill for an unheated 50-metre line |
NLGI grade is a consistency band from ASTM D217. It does not describe thickener chemistry, base-oil viscosity or whether two greases may share a housing.
Questions plants actually ask
Is NLGI 2 a better grease than NLGI 00?
No. NLGI 2 is stiffer, as measured by ASTM D217. NLGI 00 is softer so it can travel. Film strength is mostly the base-oil viscosity and the additive system, not the integer on the pail.
Can we thin NLGI 2 with oil in the pump room to get NLGI 00?
No. That changes consistency, additive concentration and often the thickener structure, and it is no longer the product that was tested. Manufacture the soft grade on purpose.
Which method shows that a centralised grease will move in winter?
Apparent viscosity, ASTM D1092, flow pressure, DIN 51805, or low-temperature penetration, ISO 13737. Use the limit your lubrication-system OEM actually cites.
Can NLGI 00 and NLGI 2 share a gun if they are different thickeners?
No. Grade does not cancel thickener incompatibility. Dual-stock inside one family, in dedicated equipment. A chart is a screen, not a guarantee.
Literature and prior art
Citations below are orientation, not a freedom-to-operate opinion. Lubechem does not copy claimed compositions and does not treat a patent as a product endorsement.
- ASTM D217 and ISO 2137 — Cone penetration. NLGI grades are bands on the 60-stroke result at 25 °C.
- ASTM D1092, DIN 51805, ISO 13737 — Apparent viscosity, flow pressure and low-temperature penetration for lines that must move when it is cold.
- ASTM D445 — Kinematic viscosity of the base oil. This is the film knob, separate from NLGI grade.
- ASTM D1478 and ASTM D4693 — Low-temperature torque screens for bearings, not a substitute for line pumpability.