What is the NLGI grade of lubricating grease?

2025-09-15

In the following article, we will explain the key properties of lubricating grease and the classification criteria for lubricating grease based on its consistency, as well as information about the NLGI.

The advantages of lubricating grease are its ability to adhere to the application area and, due to its consistency, its ability to resist the effects of gravity. Different types of grease can be distinguished based on the type of thickener, the viscosity of the base oil, and the consistency or hardness.

Grease is primarily divided into two categories: grease thickened with soap and grease thickened with other ingredients. The base oil for both types of grease can be mineral or synthetic.

The flowability of a grease depends on the viscosity of its base oil and the type and proportion of thickener used during production. Grease flowability is also affected by application factors such as temperature, pressure, shear stress, and frequency of exposure.

Here it is Worked Cone Penetration Test video from FRTLUBE Laboratory

WHAT ARE THE CRITERIA FOR GROUPING GREASES BASED ON THEIR HARDNESS?

Grease must always have the right consistency so that it adheres to the mechanical parts it lubricates without causing excessive friction. Greases are classified according to grades established by the National Lubricating Grease Institute (NLGI). The softer the grease, the lower the NLGI value. This test measures the depth a metal cone penetrates a grease sample at a given temperature. This indicates the level of fluidity in millimeters.

NLGI grade ( National Lubricating Grease Institute) NLGI consistency numbers
NLGI	ASTM worked (60 strokes)	Appearance	Consistency food analog
NLGI	penetration at 25 °C	Appearance	Consistency food analog
000	445-475	fluid	cooking oil
00	400-430	semi-fluid	apple sauce
0	355-385	very soft	brown mustard
1	310-340	soft	tomato paste
2	265-295	"normal" grease	peanut butter
3	220-250	firm	vegetable shortening
4	175-205	very firm	frozen yogurt
5	130-160	hard	smooth pâté
6	85-115	very hard	cheddar cheese

The National Lubricating Grease Institute (NLGI) is a US organization that uses the ASTM D217 method to measure and classify grease consistency. ASTM D217 provides four procedures for measuring grease hardness by penetrating a cone of specified size, mass, and finish.

NLGI Grade 000-NLGI 0 greases
Application :NLGI Grade 000-NLGI 0 are recommended for high pressure, heavy-duty and closed system.
Advantages : Outstanding lubricity performance,good pumpability,better heat dissipation.
Disadvantages: Easy to appear oil separation.

NLGI 1- 2
Normally NIGI 2 is the standard and most popular consistency in most of greases,it is normal greases. But in practical applications,different application or different equipments will be required various Nlgi Grease.
Advantages : Wide range of applications,good colloidal stability
Consistency NLGI grade ≠Viscosity
Customer ask ：i am looking for one thicker greases...
Lubircant factory ：Do you want more “harder”grease or more “stickier” grease?
Customer ：What is the difference between these two?

Firstly Nlgi Grades (Consistency &Penetration ) is only for Grease products
And viscosity is for lubricating oils or the base oils of greases products.
NLGI grades classify grease soft or hard ,it stand for grease appearance state.
viscosity classify grease base oil viscosity,It determines the grease viscosity，The higher the viscosity,and the grease is more stickier.

Normally 2 greases may have same NLGI grade but very different base-oil viscosities, while two others might have the same base-oil viscosity but dissimilar NLGI grades，that is normal situation in greases products.
That is why we had to understand well customer’s real demand.