The NLGI consistency number expresses a measure of the relative hardness of a grease used for lubrication, as specified by the standard classification of lubricating grease established by the National Lubricating Grease Institute. The NLGI consistency number (sometimes called “NLGI grade”) expresses a measure of the relative hardness of a grease used for lubrication, as specified by. NLGI is a not-for-profit organization that serves the lubricating grease industry. The NLGI number is a measure of the grease's consistency as indicated by its worked penetration value. February 17, 2017 - NLGI Grade. What does it mean when your grease has an NLGI Grade 00? In order to help the layman understand them, we've included a chart here that compares NLGI.