Choosing the Right Grease

Richard L. Parish, PhD, PE

Most larger lawn and garden equipment requires regular lubrication with grease. Putting the correct grease in your grease gun and using it religiously can prolong the life of your equipment. Grease can be categorized several ways. You want a grease good enough to meet manufacturers' specifications and protect your equipment, but that might not require the most expensive grease. When you buy grease, you will be faced with a range of choices. Here is some help in deciding what to use.

Composition of Grease: Lubricating grease consists basically of oil and a thickening agent that keeps the oil suspended, similar to water in a sponge. When the grease is under pressure, the oil is squeezed out and lubricates the parts; when the pressure is released, the oil is reabsorbed. The thickness of the grease is described by a scale from 000 to 6, where 000 is a heavy oil and 6 is a solid "brick grease." A rating of 2 is common for agricultural and lawn/garden/grounds maintenance equipment.

Thickeners can be classed as "soap-based" (lithium) or "nonsoap" (synthetic). The lithium or soap-based greases are more common, but require a higher percentage of thickener to do the same job. Nonsoap greases might be a better choice for sealed-for-life applications, but lithium greases are fine for most purposes.

NLGI Rating: The National Lubricating Grease Institute (NLGI) rates grease for two types of service: wheel bearing (G) and chassis (L). Each is further classified into three performance levels (A, B, and C) ranging from mild duty (A) to severe duty (C). A typical grease suitable for many agricultural and lawn/garden/grounds maintenance machines would be rated number 2 GC-LB.

Additives: Many additives can be used in grease, including graphite and molybdenum disulfide. These can enhance performance and help under extreme pressure.

Viscosity: The viscosity of the grease should be matched to the application. Low viscosity greases are needed for high-speed applications to enhance flow, while slow-moving components benefit from a high viscosity grease.

Grease Gun: In most cases, you will need a grease gun to pump the grease under pressure into fittings called "zerks." Hand grease guns come in several types. Small guns are available for lawn and garden use, but don’t hold much grease and the cartridges are expensive. Full-size grease guns are available in pistol-grip (for one-handed operation) and lever-action (requiring two hands). You will generally need one hand to hold the hose on the zerk while pumping, so unless you are blessed with three hands, a pistol-grip grease gun is a better choice. Power grease guns are available, but generally not practical for individuals.

A good overall grease for lawn/garden and grounds maintenance equipment will be rated number 2 GC-LB. This may contain additives. You should check your operator's manual for specific recommendations for your equipment and use the recommended grease. A good pistol-grip grease gun will make application easier.