Grease is the most misunderstood product on most lubricant price lists. Buyers who will debate SAE viscosity grades for an hour will order "grease, NLGI 2" without checking the thickener, dropping point or base oil viscosity — the three things that determine whether it survives in service. In Indian operating conditions, where ambient heat, monsoon water ingress and airborne dust all attack a grease at once, that gap costs bearings.
This guide covers what the NLGI grease grades mean, how the major thickener chemistries differ, why dropping point and base oil viscosity are separate decisions from consistency, and how to select for the specific stresses of Indian and tropical export markets. Axabull manufactures its grease range in Surat, Gujarat, alongside a full automotive and industrial lubricant catalogue.
What the NLGI grade actually measures
The National Lubricating Grease Institute (NLGI) classifies grease by consistency — how stiff or soft it is — and nothing else. Consistency is measured by ASTM D217 worked penetration: a standard cone is dropped into a worked sample of grease for five seconds at 25°C, and the depth it sinks is recorded in tenths of a millimetre. A deeper number means a softer grease. Each NLGI grade covers a 30-point penetration band.
This is the single most important thing to understand about the number on the pack: an NLGI 2 grease can be excellent or useless depending on its thickener and base oil. The grade tells you how it will pump and stay in place, not how hot it can run or how much load it will carry.
| NLGI grade | Worked penetration (ASTM D217, 0.1 mm) | Texture | Typical application |
|---|---|---|---|
| 000 | 445–475 | Fluid | Enclosed gearboxes and centralised systems needing near-oil flow |
| 00 | 400–430 | Semi-fluid | Long-line centralised lubrication, leaky or worn gear cases |
| 0 | 355–385 | Very soft | Cold-climate centralised systems, low-torque bearings |
| 1 | 310–340 | Soft | Long pumped distribution lines, chassis systems, low ambient temperatures |
| 2 | 265–295 | Medium (buttery) | General purpose — wheel bearings, electric motors, most rolling bearings |
| 3 | 220–250 | Firm | High-speed or vertically mounted bearings, prevention of leakage and throw-off |
| 4 | 175–205 | Very firm | Heavily loaded slow bearings, some sealed-for-life and open-gear uses |
| 5 | 130–160 | Hard | Specialised heavy plant and open gearing |
| 6 | 85–115 | Block hard | Block grease for slow, hot plain bearings; cut and placed by hand |
In practice, NLGI 2 accounts for most grease consumed worldwide, with NLGI 3 used where leakage or throw-off is the concern and NLGI 0 and 00 reserved for centralised systems pumping down long lines.
Thickener chemistry: the decision that matters more than the grade
The thickener is the sponge that holds the base oil. It sets the grease's temperature ceiling, water resistance and compatibility with whatever is already in the bearing. These are the chemistries you will encounter.
- Lithium soap — the traditional general-purpose thickener. Good mechanical stability, decent water resistance, dropping point typically around 180–200°C, so a practical continuous limit near 120–130°C. Economical and widely compatible. Weakness: it loses structure quickly if it is repeatedly taken near its dropping point.
- Lithium complex — lithium soap plus a complexing acid, which pushes the dropping point to roughly 260°C or above and improves mechanical and water stability. The modern default for high-temperature automotive and industrial multi-purpose grease. Weakness: costs more than simple lithium, and it is not a licence to ignore relubrication intervals.
- Calcium (conventional hydrated) — excellent water resistance and cheap, which is why it persists in chassis and water-pump applications. Weakness: a low dropping point, around 95–105°C, because the structure depends on water that boils off. Unsuitable for anything that runs genuinely hot.
- Calcium sulphonate complex — outstanding water washout resistance, inherent rust protection and inherent extreme-pressure performance without heavy EP additive loading, with a dropping point often above 300°C. The premium choice for wet, corrosive and heavily loaded service. Weakness: price, and it can be stiffer to pump in cold conditions.
- Polyurea — a non-soap thickener with excellent oxidation life and a dropping point around 240–260°C, which is why it dominates sealed-for-life electric motor bearings. Weakness: notoriously poor compatibility with many soap greases, so never top up a polyurea bearing with lithium grease without purging.
- Bentonite / organoclay — a non-melting clay thickener with no true dropping point, useful for very high temperature applications such as kiln and oven bearings. Weakness: oxidation life of the base oil, not the thickener, becomes the limit, and mechanical stability under heavy shear is only moderate.
Two greases can both be NLGI 2 and be completely wrong for each other's application. Specify the thickener as deliberately as you specify the grade — and never mix chemistries in the same bearing.
Dropping point is a limit, not an operating temperature
The dropping point (ASTM D566 or D2265) is the temperature at which a grease becomes fluid enough for a drop to fall from a test cup. It is a quality-control indicator of the thickener type, not a service rating. A sensible working rule is to keep continuous operating temperature well below the dropping point — commonly 60 to 100°C below. A lithium complex grease with a 260°C dropping point is not a 250°C grease; it is a robust general-purpose grease with headroom for the hot spots and heat soak that real equipment produces.
The mistake most buyers make: consistency versus base oil viscosity
This is where selection most often goes wrong. NLGI grade and base oil viscosity are independent variables, and it is the base oil viscosity that actually forms the lubricating film between rolling elements. A soft NLGI 1 grease built on a heavy 460 cSt base oil will protect a slow, heavily loaded bearing far better than a firm NLGI 3 grease built on a light 100 cSt oil — even though the NLGI 3 feels much more substantial in your hand.
The rule of thumb is straightforward:
- High speed, light load, cooler running — lower base oil viscosity, typically ISO VG 68 to 150. Heavy oil generates churning drag and heat.
- Low speed, heavy load, shock loading — higher base oil viscosity, typically ISO VG 220 to 460 or above, to maintain film thickness at low entrainment speed.
- Choose NLGI grade for how the grease must be delivered and retained — pumped through a long centralised line, held in an open housing, or resisting throw-off at speed.
Ask any supplier for the base oil viscosity on the technical data sheet, not just the NLGI number. If it is not published, that tells you something about the product.
EP additives and water washout
Two further properties decide whether a grease survives real service. Extreme pressure (EP) additives, typically sulphur-phosphorus compounds and often assessed by four-ball weld load and Timken OK load, create a sacrificial film that protects surfaces under shock and boundary-lubrication conditions. Wheel bearings under braking, agricultural pins and bushes, and steel plant rolls all need EP performance. General-purpose non-EP grease in those points will fail early.
Water washout resistance (ASTM D1264) measures how much grease is flushed out of a bearing by water at temperature. It is the property that separates greases that survive an Indian monsoon from those that emulsify and run out of the housing. Calcium sulphonate complex is strongest here, lithium complex with rust and oxidation inhibitors is a solid middle option, and conventional lithium is the weakest of the three.
Grease selection table by application
| Application | NLGI grade | Thickener | Key property to specify |
|---|---|---|---|
| Automotive wheel bearings | 2 | Lithium complex | High dropping point plus EP for braking heat and shock load |
| Chassis, pins and bushes | 1–2 | Lithium or lithium complex | Pumpability through grease guns plus adhesion and rust protection |
| Agricultural and construction equipment | 2 | Lithium complex | EP performance, dust resistance and heavy base oil viscosity (VG 220+) |
| Steel plant and high-temperature bearings | 2 | Lithium complex, calcium sulphonate or bentonite | Dropping point above 260°C and strong oxidation life |
| Marine, pumps and water-exposed points | 2 | Calcium sulphonate complex | Water washout resistance and inherent corrosion protection |
| General industrial rolling bearings | 2 | Lithium or lithium complex | Base oil viscosity matched to bearing speed and load |
| Electric motor bearings (sealed) | 2–3 | Polyurea | Long oxidation life; never top up with a soap-thickened grease |
| Centralised lubrication systems | 0–00 | Lithium or lithium complex | Low-temperature pumpability over long distribution lines |
Why Indian conditions change the answer
A grease specification borrowed from a temperate market will underperform in India and in most of the tropical export markets served from here. Three environmental factors dominate.
Sustained high ambient temperature
Equipment that starts the day at 40°C ambient reaches bearing temperatures a European specification never anticipated, and oxidation rate roughly doubles for every 10°C rise. That alone is the argument for lithium complex over conventional lithium in most Indian automotive and industrial points: the extra dropping-point headroom and better oxidation life directly extend relubrication intervals rather than just looking better on a data sheet.
Monsoon water ingress
Four months of driving rain, flooded yards and washdown cycles put water into housings that are theoretically sealed. Conventional calcium grease handles the water but not the heat; conventional lithium handles the heat but washes out. Lithium complex with rust and oxidation inhibitors covers most duty, and calcium sulphonate complex is the right specification for genuinely wet service such as pumps, marine equipment and exposed agricultural machinery.
Dust loading
Abrasive dust from unpaved roads, quarries, cement and agricultural work is a grinding paste once it enters a bearing. The counter-measures are a slightly firmer grease that forms a better collar seal at the housing, adequate purge volume during relubrication, and shorter intervals in severe service. This is one of the few cases where moving from NLGI 2 to NLGI 3 is genuinely justified.
Sourcing grease in bulk
For distributors, importers and maintenance buyers, the practical checklist before you order is short: confirm the thickener type, confirm the dropping point, confirm the base oil viscosity, confirm whether EP additives are present, and ask for the TDS and MSDS on every SKU before the container is booked. Get those five answers and you can specify grease as confidently as you specify engine oil.
Axabull manufactures greases alongside its automotive lubricants and industrial fluids range from its plant in Surat, Gujarat, refining from imported Group II+ base oils, and supplies both branded and private-label bulk volumes. The company exports to 16 countries across the Middle East, South Asia, Africa, the Caribbean and South America through an overseas hub in Sharjah, UAE — markets that share the heat, humidity and dust loading described above.
To discuss grades, pack sizes and bulk or private-label supply, browse the grease range, then start an international enquiry on the global B2B and export page or reach the team directly through the contact page. Tell us the application, the operating temperature and the load, and we will recommend the grade and thickener rather than simply quoting the cheapest NLGI 2 on the list.