What do the NLGI numbers mean?
NLGI stands for National Lubricating Grease Institute
It is a measure of the thickness of the grease. There are 9 measured thicknesses from 000 which is fluid to 6 which is solid.
This is measured by dropping a cone-shaped solid into a cup of grease at 25 Deg C. The depth of the displaced grease is then measured and is corresponded with an NLGI thickness.
What is the difference in greases apart from thickness?
Grease is a mixture of base oil, thickener, and additive. Like all lubricants such as engine oil, different greases are blended for different applications.
These are tailored toward 4 main principles:
Some greases are required to carry heavy loads, others to resist high temperatures, and others to work in extreme environments. Like most lubricants, some greases can work across several areas and some are made for specific purposes which are why there are many types available.