NLGI

NLGI stands for the National Lubricating Grease Institute, a trade association of grease manufacturers and suppliers in the United States. Founded in the 1930s, it develops and promotes standard practices for lubricating greases, including a widely used consistency classification system that bears its name.

The NLGI grade is a standard measure of grease consistency. It assigns a number from 000 to 6 to a grease based on its worked penetration in the ASTM D217 test. Softer greases have lower numbers; stiffer greases have higher numbers. The grade is used in product specifications to guide selection for particular applications, operating temperatures, loads, and speeds. The most common grade is NLGI 2, but other grades (from very soft 000 or 00 up to very stiff 4 to 6) are used in specialized service. Labels typically include the NLGI grade along with base oil, thickener type, and temperature rating.

Scope and impact: NLGI provides standard test methods and guidance to ensure comparability of grease products. It is widely recognized internationally, and its classification system is embedded in many procurement specifications, supplier data sheets, and equipment manufacturer recommendations. The system helps engineers and technicians select appropriate greases for bearings, gears, and other lubrication points across a range of industries and operating conditions.