Larry Crider
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Well the short answer is that grease is a lubricant added to a thickening agent to form a semi-solid lubricating product and that’s an okay answer but really…grease is sooo much more!   
Human beings have been lubricating (greasing) things for millennia. The earliest greases were simply animal and vegetable fats. And guess what! These sorts of greases are still used for certain things.   

These days though when someone asks about lubricating grease they are usually referring to a product used to lubricate closed bearing systems or other closed or hard to lubricate devices such as pivot points on steering gear or heavy equipment.   

The base oil or lubricant portion of grease is most commonly either petroleum or synthetic oil of varying viscosities although there are other less well know base lubricants used in grease, mostly for industrial applications such as silicones and flouroether’s   

The base oil of grease is generally the first consideration when choosing grease for a particular application. The things to be considered when choosing grease are, operating speed, the temperature range that the machinery operates and total load.   

Now on to thickening agents, the stuff that makes a base oil “look” like grease.  By far the most common thickening agent is lithium soap, the term “soap” indicating a metallic salt of a fatty acid. This metallic salt forms an emulsion with the base oil, meaning they are mixed together but not chemically combined.   

Aside from lithium, there are many different thickening agents that allow grease to be tailored for thousands of different applications. These include other metallic soaps such as calcium, sodium and, aluminum.   

These in turn can be mixed with complexing agents to form lithium complex, calcium complex or aluminum complex greases. Complexing agents add stability and performance increases like increasing the high and low temperature performance of the grease or make it more water resistant.   

Some non-metallic soap thickening agents are various polymers, polyurea’s, organic clay’s, silica and carbon black   Now on to the additive package. When grease is designed various additive are mixed in to make the grease work well under different conditions.    

Marine grease designed for a salt water environment for example will incorporate powerful rust and corrosion inhibitors. Grease used in high temperature applications will often incorporate oxidation inhibitors to keep the grease from degrading under the effects of heat. Grease’s meant for extreme pressure situations will generally include some form of solid lubricant such as molybdenum or graphite. The solids form a sacrificial layer under extreme pressure and high loads that help prevent metal to metal contact and the attendant wear that causes.   

Grease that is designed to be used on open gears or unsealed hinge points will sometimes incorporate a takifying agent to cause it to cling to the metal surface and not be slung off in the case of open gears or squeezed out so readily in the case of hinge points on equipment that have high loads such as the hinge points on the arm of a backhoe.   

Actually, properly formulated grease’s will usually have a combination of these additives. Oxidation inhibitors, rust and corrosion inhibitors, anti-wear ingredients like zinc or extreme pressure additives like molybdenum to make the finished product a well rounded one that performs its function well.   

A great example of  well rounded grease designed for a specific commercial use is Amsoil’s new synthetic polymeric off road grease which combines an over-based calcium-sulfonate complex thickener and proprietary synthetic polymeric technology to provide incredible  performance in heavy duty off-road applications such as earth moving, mining and construction equipment.  

Greased components on this type of heavy equipment are subjected to high loads accompanied by impact and shock loading. The heavy high impact loads common to off-road equipment forces all of that load (pressure) onto places where the equipment pivots, relying on the grease to prevent metal-to-metal contact. 

So you can see that grease is not just gooey stuff in a tube or can but a highly engineered lubricant designed to do specific things for the demands of specific applications.   

Amsoil Inc introduced the first full synthetic motor oil to meet American petroleum institute requirements in 1972. Today Amsoil is considered the world leader in synthetic motor oils and lubricants for all types of applications.   

By Larry Crider

 Corpus Christi, TX 78411