"What should you look for in a good grease?"
When selecting a grease, you must consider the application and operating conditions in which the grease will function. For a better understanding of what goes into a good grease, concentrate on its components, including the base oil type, thickener type and base oil viscosity.
Base oil viscosity is one of the most important properties of any lubricant and is often overlooked and misunderstood when it comes to grease. The base oil viscosity for bearings can be calculated using a formula that takes the speed and dimensions of the bearing into consideration. It is critical to understand a grease’s base oil viscosity in order to choose the right grease for the application and conditions. Typically, a general-purpose grease will have a viscosity of ISO 460 or higher.
The base oil type is determined by the conditions in which the grease will perform, such as high and/or low temperatures, load and pressure. The load and pressure not only will influence the base oil type but also the additive package (extreme pressure, anti-wear, etc.). While synthetic oils will be better over a wider range of temperatures and conditions, mineral base oils can be used if you have a more constant running temperature.
Most people believe the thickener is the lubricating part of the grease, but it actually is what holds the lubricant in place, like a sponge. A good thickener type will be compatible with the equipment manufacturer recommendations and will be able to withstand the conditions under which it must perform. There are many types of thickeners, but most are not compatible and should not be mixed. The most common thickeners are lithium, lithium complex, aluminum complex and polyurea.
Keep in mind that grease can be employed in a variety of machines, operations and conditions. Some of the more popular uses of grease are for cables, plain bearings, rolling-element bearings, linear bearings, ball screws, slideways and seals. All of these components are in machines that may be operating in the extreme heat and dust of a desert in Australia or subzero temperatures on a fishing trawler in the middle of the Atlantic Ocean.
As you can see, there are many different types of applications and environments and just as many types and brands of grease to go along with these machines and conditions. Therefore, a good grease will be the one that best works for you and your machinery.