Grease Consistency/ Penetration


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The respective stiffness level (or softness) of a grease is measured by an instrument called a penetration meter.  A steel cone is ‘dropped’ into the grease sample, and the penetrating depth of the cone is measured.  A deep intrusion of the cone into the grease signifies a soft grease, while a shallow penetration indicates a harder grease.

grease consistency

To simplify grease selection, the National Lubricating Grease Institute (NLGI), classified stiffness according the cone depth penetration levels, as illustrated on the table below.

classified stiffness according the cone depth penetration levels

Stiffer greases, NLGI 3 or higher, are recommended for applications where adhesiveness is paramount, such as with bearings under very high vibrations and shock loads, or open bearings exposed to the environment.

Softer semi-flowing greases such as NLGI 000, and 00, are used for open gear systems wherein greases are sprayed, or used as a bath.

NLGI 0 and 1 greases are appropriate for automatic lubricating systems, while NLGI 2 is the standard consistency most consistently used.

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