What does the NLGI classification of a lubricating grease mean?

When you see NLGI 2 or NLGI 00 on a grease container, you may wonder what those numbers mean. The NLGI classification is an international standard that indicates how thick or fluid a grease is. It plays an important role in choosing the right lubricant for each application.

What is NLGI?
NLGI stands for National Lubricating Grease Institute, an American organisation that has been setting guidelines for the quality and consistency of lubricating greases since 1933. Their classification system helps users worldwide to compare greases based on consistency, i.e. how firm or fluid the grease is.

How is the NLGI class determined?
The NLGI class is measured using a penetration test. This involves placing a standardised cone in the grease and measuring how deep the cone sinks. The further the cone sinks, the softer the grease is.
The measurement results in an NLGI number between 000 (very fluid) and 6 (very hard).

How do you choose the right NLGI class?
The choice depends on temperature, speed, load and lubrication system:

Low temperatures or automatic lubrication → use a softer grease (NLGI 0 or 00).
High temperatures or high load → choose a firmer grease (NLGI 2 or 3).
General industrial and automotive applications → usually NLGI 2, the “universal” choice.
For example:
Super Lube Multi-Purpose Synthetic Grease is an NLGI 2 grease, ideal for bearings, hinges and gears in a variety of conditions.

The NLGI classification does not indicate the type of thickener (such as lithium or calcium) or the base oil (mineral or synthetic), but only the consistency. Nevertheless, it is a crucial first step in selecting the right grease.

A well-chosen NLGI class ensures optimal lubrication, reduces wear and tear and extends the service life of your machines.