Formulation Guide

Grease Formulation Explained — Thickeners, NLGI Grades and Selection

A grease is base oil held in a thickener, plus additives. The thickener chemistry sets the temperature range, water resistance and life; the NLGI grade sets the consistency; the base oil and additives set load and speed capability. This guide covers each thickener family, how NLGI grades work, and how to select the right grease.

In short: grease is roughly 70–95% base oil, 3–30% thickener and a few percent additives. The thickener behaves like a sponge — it holds the oil in place and releases it under load and temperature, so a grease stays put where an oil would drain away. Choosing the thickener, NLGI grade, base-oil viscosity and additives to match temperature, load, speed and water exposure is the core of grease formulation — one branch of how lubricants are formulated.

Thickener chemistries

Lithium & lithium complex

The workhorse thickeners. Simple lithium 12-hydroxystearate gives a smooth NLGI 2 grease with a ~190 °C dropping point; lithium complex pushes the dropping point above 260 °C for higher-temperature, heavier-duty service. Lithium Grease → · Lithium Complex →

Calcium & calcium sulfonate

Calcium soap greases are naturally water-resistant. Overbased calcium sulfonate complex greases have no true dropping point and deliver inherent EP, rust and water resistance without added additives. Calcium Soap Grease → · Calcium Sulfonate (CaSX) →

Aluminium, barium & sodium

Aluminium complex is clear and food-compatible with good water resistance; barium complex resists water and chemicals; sodium soap is fibrous and high-temperature but not water-resistant. Aluminium Complex → · Sodium Soap →

Non-soap: polyurea, clay & PFPE

Polyurea is a long-life, oxidation-resistant thickener favoured for sealed-for-life electric-motor bearings. Bentonite clay is non-melting for high heat. PFPE (PTFE-thickened) survives extreme chemical and temperature environments. Polyurea Grease → · PFPE Grease →

NLGI consistency grades

The NLGI grade describes how hard or soft a grease is, measured by ASTM D217 worked penetration. Softer grades pump and channel easily; harder grades stay in place under load and at speed.

NLGI grade	Worked penetration (0.1 mm)	Typical use
000 – 0	445 – 385	Centralised systems, gearboxes (semi-fluid)
1	310 – 340	Low-temperature, centralised lubrication
2	265 – 295	General-purpose — most bearings (standard)
3	220 – 250	High-speed / vertical bearings, sealed units
4 – 6	175 – 85	Block grease, special heavy-duty

How to select a grease

Match four things to the application: temperature (dropping point and oxidation stability of the thickener/base oil), load (EP/AW additives and NLGI grade), speed (base-oil viscosity and the bearing speed factor), and environment (water, chemicals, food contact). Getting this right — and validating it against ASTM tests — is what grease formulation, ASTM testing and grease plant setup deliver.

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Frequently asked questions

What is grease made of?

Grease is a base oil (typically 70–95%) held in a thickener (about 3–30%), plus performance additives. The thickener acts like a sponge that releases oil under load and holds it in place, so grease stays where oil would drain away.

What does the NLGI grade mean?

NLGI grade is the consistency (hardness) of a grease, set by ASTM D217 worked penetration. It runs from 000 (near-fluid) to 6 (block). NLGI 2 (penetration 265–295) is the general-purpose standard for most bearings.

Which grease is best for high temperature?

It depends on the dropping point and base-oil oxidation stability. Lithium complex (>260 °C), calcium sulfonate complex and bentonite clay (no true drop point) and polyurea all serve 150–220 °C+ applications far better than simple lithium or calcium soap greases.

What is the difference between soap and non-soap greases?

Soap greases (lithium, calcium, sodium, aluminium and their complexes) are made by saponifying a fatty acid with a metal hydroxide. Non-soap greases (polyurea, bentonite clay, PFPE) use organic or inorganic thickeners and often give better high-temperature life and oxidation resistance.

Can I mix two different greases?

Often no. Thickeners can be incompatible — mixing can soften or harden the grease and drop the effective dropping point, causing leakage or bearing failure. Always check thickener and base-oil compatibility before topping up with a different grease.

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