Greases may show deterioration in one or more of the following ways:
Excessive oil separation
Some “bleed” is normal and required
Significant change (>25 percent) in the grease consistency as measured by worked or unworked penetration. Grease consistency affects the ease of grease application, low-temperature performance and stay put performance, all critical characteristics ensuring proper grease lubrication. In technical terms, grease’s consistency is referred to as its NLGI Grade – from NLGI 000 (semifluid) to NLGI 6 (block – very firm)
Significant change in color or odor
Noticeable change in texture