A numerical scale for classifying the consistency of lubricating greases, based on the ASTM D217 worked penetration at 25°C (77°F). NLGI Grades are also referred to as NLGI Consistency Numbers or NLGI Numbers. In order of increasing consistency (hardness):
|NLGI Grade||Worked Penetration Range, 25 °C (77 °F)|
Some grease suppliers use descriptions such as NLGI Number 1.5, which indicates that the grease is between NLGI Numbers 1 and 2.