Greases

Grease is not just very thick (viscous) oil, it is thickened oil. This distinction is important because there are many different thickeners and they affect the performance of the grease differently.

The thickener in the grease acts like a sponge that holds the oil. When the grease is stressed (when squeezed between moving surfaces) the thickener releases the oil, which then lubricates the moving surfaces. Once the stress is relieved the thickener soaks up most of that oil again. 

All greases contain a thickener and most thickeners are incompatible with each other. If one were to mix greases with different thickeners the resulting mixture would probably not perform as expected. 

A grease that has been stored indoors, out of direct sunlight and at moderate temperatures in the original sealed container can have a shelf life of about 5 years.

These numbers usually refer to the NLGI rating of a grease. A grease with an NLGI rating of 1 is more fluid than a grease with an NLGI rating of 2 or 3. The smaller the NLGI number, the more fluid the grease is.

There need not be any difference between these greases. The colour is created by a dye which is added during manufacturing. The dye does not affect or determine the performance of the grease. Dyes are added to greases to make them easier to distinguish from one another.