Most people have a can of grease in their garage or shop but don’t know what it is, what it does, or how to use it. This guide will teach you the basics of grease, including grease types and grades.
Grease is a substance used to lubricate, protect and seal machine components. It is made up of base oil, thickener, and additives. The base oil can be of mineral, synthetic or natural origin, while the thickener can be soap-based or non-soap-based.
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What is Grease?
Grease is a semisolid lubricant. It is a combination of an oil and a thickener (soap) used as a lubricant for bearings, joints, and other moving parts. The main purpose of using grease is to keep moving parts well-lubricated and protected from corrosion.
There are many different types of grease, each with its own unique properties and uses. Grease is classified by its thickness (or viscosity), soap type, operating temperature range, and additives.
Thickness (or viscosity) is measured by the NLGI (National Lubricating Grease Institute) scale, which goes from 000 (very thin) to 6 (very thick). The lower the number, the thinner the grease; the higher the number, the thicker the grease.
The thickness of a grease affects how well it flows and how long it lasts in service. A thicker grease will generally last longer than a thinner one, but it may be too stiff to flow easily in cold temperatures. Conversely, a thinner grease may flow better in cold temperatures but won’t last as long in service.
Soap type refers to the type of soap used to thicken the oil. The most common types are lithium soap, calcium soap, and sodium soap. Each type has different properties that make it suited for different applications. For example, lithium soap-based greases are good for high-temperature applications because they have a low melting point.
Calcium soap greases are good for heavy-duty applications because they have excellent wear resistance properties. Sodium soaps are good for general-purpose applications because they are water-resistant and have good rust protection properties.
The operating temperature range is the temperature range over which a particular grease can be used without deterioration.
Best Grease for different Applications
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Most greases have an operating temperature range of -20°C to +120°C (-4°F to +248°F), but there are specialty greases that can operate in much higher or lower temperature ranges (-54°C to +177°C/-65°F to +350°F). When choosing a grease, always select one with an operating temperature range that exceeds the highest temperature that will be encountered in service.
Additives are chemicals that are added to base oils to improve the performance of the finished grease in specific applications or under specific conditions.
Some of the most common additives include:
- Antioxidants – extend grease life by preventing oxidation;
- Rust inhibitors – protect metal surfaces from rust;
- Extreme pressure additives – improve wear protection;
- Anti-wear additives – improve wear protection;
- Anti-foam additives – prevent foaming;
- Viscosity index improvers – maintain viscosity at high temperatures;
- Pour point depressants – keep grease flowing at low temperatures.
Functions of Grease
Grease is a semisolid lubricant. There are many types of grease, each designed for specific purposes. Grease generally consists of a soap emulsified with mineral or vegetable oil. The main functions of grease are to:
- Prevent metal-to-metal contact between moving surfaces
- Reduce friction and wear
- Protect metal surfaces from corrosion
- Seal out water and other contaminants
- Carry away heat
Properties of Grease
Grease is a semisolid lubricant. It consists of a soap emulsified with mineral or synthetic oil. The characteristic feature of a grease is that it retains its lubricating qualities during periods of inactivity or under heavy loads. Grease does not flow like liquid lubricants, and it is not easily vaporized like oils. Grease generally cannot be used at temperatures over 300°C (570°F).
Most greases are formulated with a mineral oil base; however, some are made with synthetic oils such as polyalphaolefin (PAO), polybutene (PB), or silicone oil. The type of oil selected depends on the operating temperature range and the environment in which the grease will be used.
Grease Types and Grades
Grease Grades
Greases are classified by their thickness or consistency. The International Organization for Standardization (ISO) has established standards for measuring grease consistency. Greases are classified by their NLGI grade, which ranges from 000 (fluid) to 6 (very hard). The lower the NLGI number, the thinner the grease; the higher the number, the thicker the grease.
The term “grease” is often used to mean all lubricating greases, even though liquid lubricants are sometimes called greases. The American Society for Testing and Materials (ASTM) defines lubricating grease as “a solid or semisolid lubricant consisting of a soap emulsified with suitable mineral or synthetic oil.
NLGI Grades
Grease is assigned an NLGI consistency grade from 0 to 6. The lower the NLGI number, the softer or thinner the grease. The higher the number, the harder or stiffer the grease. The table below shows NLGI grades along with corresponding penetration and worked penetration numbers.
NLGI Grease Consistency
- Sawdust-like, will not pack
- Very soft, packs under light finger pressure
- Soft, packs under moderate finger pressure
- Moderately soft, packs easily
- Medium consistency, neither hard nor soft
- Moderately hard, difficult to pack
- Hard, cannot be packed
ISO Grades
Grease is a semisolid lubricant. It consists of a soap emulsified with mineral or synthetic oil. The characteristic feature of greases is that they possess a high initial viscosity, which upon the application of shear, reduces progressively to give the effect of an oil-lubricated bearing of approximately the same viscosity as the base oil used in the grease. In general, greases are used when lubrication requirements exceed those for oils but are insufficient to justify permanent lubrication by an oil system.
There are ISO and Aggressive Environment Grease (AEG) grades for molybdenum disulfide (MoS2) thickened greases and AEG grades only for graphite thickened greases. The former is used where the good load-carrying capacity and EP performance combined with excellent resistance to water washout is required while the latter is designed to give maximum protection against wear, even in heavily contaminated or hot environments where conventional greases would fail rapidly.
Related Guide: What are the Composition, Functionality, and Characteristics of Grease Lubricant (2023 – 2024)? [Explained!]
Grease Types
Grease is a lubricating material composed of soap and one or more oils. The primary function of grease is to reduce friction and wear in bearings. Grease can also be used to seal and protect exposed metal surfaces from corrosion.
Lithium Grease
Lithium grease is a type of grease that is made with lithium soap and can offer high-temperature resistance. It is also waterproof and resists wash-out. This type of grease is used in a variety of applications, including automotive, marine, and industrial applications. It is also used in some household applications.
Best Grease for Various Uses
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Lithium Complex Grease
Lithium complex greases are NLGI grade 2, 3, or 4. They have a good balance of properties for general-purpose grease applications. Whilst they cover a fairly wide temperature range, they are not suitable for very high or low temperatures as they will break down relatively quickly.
They are also not recommended for applications where there will be high water contamination as they will absorb water and can break down, leading to corrosion.
Calcium Grease
Calcium greases are the most widely used type of grease and are suitable for a wide range of applications. They are made from a calcium soap thickener and mineral oil. Calcium greases have good resistance to water wash-out, making them ideal for use in wet or washdown environments.
They also have good high-temperature performance, making them suitable for use in hot conditions. However, calcium greases can be difficult to pump at low temperatures and can solidify at extremely low temperatures.
Sodium Grease
Sodium Grease, NLGI Grade 2 is a general-purpose grease recommended for medium to heavy-duty applications where extreme pressures are not encountered. It provides good rust protection and has moderate resistance to water wash-out. This grease is often used where the operating temperature is above 180°C (356°F).
Aluminum Grease
Aluminum grease is a type of grease that is made with a soap base and has aluminum added to it. This grease is used in applications where high temperatures are a concern. The aluminum helps the grease to withstand higher temperatures without breaking down.
Polyurea Grease
Polyurea grease is grease made from base oil, a thickener, and polyurea. Polyurea is a polymer that has both urea and amide functional groups in the main polymer chain. The synthesis of polyurea starts with diisocyanates which can be reacting with various diols and diamines to give the main polyurea chain.
After the main chain is formed, it can be reacted with various curatives to crosslink the main chain and form the finished polymer. The base oil for polyurea greases is generally a hydrocarbon oil with good oxidation stability such as mineral oil or synthetic hydrocarbon oils such as PAO or PAG. The thickener for polyurea greases is generally a metal soap such as lithium soap, sodium soap, or calcium soap.
The metal soaps used in polyurea greases are generally lithium 12-hydroxy stearate, sodium stearate, or calcium stearate. Polyurea greases are general-purpose greases that have good high-temperature performance and good oxidation stability. They are often used in applications where temperatures exceed the operating range of conventional lithium greases such as automotive wheel bearings.
Grease Application
Industrial and automotive greases are usually composed of a soap emulsified with mineral or synthetic oil. The oil-soap interface provides a high-energy surface that can bear significant loads.
Automotive Grease
Automotive grease is a type of grease that is specifically designed for use in automotive applications. Grease is a semisolid lubricant that is used to keep moving parts in an automobile well-lubricated and free from corrosion. Automotive grease is usually made from a soap base, oil, and additives.
The most common types of automotive grease are lithium-based greases, which are widely used because of their good thermal and shear stability. Lithium-based greases are available in a variety of grades, from light to heavy duty. Other types of automotive grease include silicon-based and sodium-based greases, which are less common but have specific advantages for certain applications.
Marine Grease
Marine grease is a type of grease that is specifically designed for use in maritime applications. It is typically made with a thickener that allows it to withstand the harshness of the marine environment, as well as extreme temperatures and high levels of humidity. Marine grease is also designed to protect against rust and corrosion, making it an ideal choice for boat owners.
Industrial Grease
Industrial grease is a thickener and oil-based lubricant used in heavy-duty applications. The base oil is usually mineral oil, synthetic oil, or a mixture of the two. Additives are used to improve performance, stability, and durability. The National Lubricating Grease Institute (NLGI) grades grease on a scale from 000 to 6, with 6 being the thickest.
The most common types of grease are listed below.
- Heavy duty: Used in construction equipment, this type of grease can withstand high loads and extreme temperatures. It is usually NLGI grade 2 or 3.
- Multi-purpose: This type of grease can be used in a variety of applications including bearings, wheel bearings, shock absorbers, and U-joints. It is usually NLGI grade 2.
- Chassis: Used in wheel bearings and suspension systems, this type of grease is designed to withstand extreme temperatures and vibration. It is usually NLGI grade 2 or 3.
- High temperature: Used in ovens, kilns and other high-temperature applications, this type of grease can withstand temperatures up to 500 degrees Fahrenheit (260 degrees Celsius). It is usually NLGI grade 2 or 3.
Grease Maintenance
The first rule of grease maintenance is to ensure that you are using the right type and grade of grease. Not all greases are created equal and some are not compatible with certain types of equipment. For example, some greases are designed for high-speed applications while others are designed for low-speed applications. The wrong grease can cause equipment failures, so it is important to get it right.
Grease Storage
Grease storage should be in a cool, dry location. An unheated garage or shed is ideal. If you must store grease inside, put it in a leak-proof container and keep it away from any heat source. Check your grease regularly for signs of spoilage, such as a change in color or texture, and discard it if it looks or smells bad.
Grease Handling
Grease is a type of lubricant that is made up of a base oil and a thickener. The base oil can be either mineral or synthetic, while the thickener can be soap-based, clay-based, or other types of thickener. Grease is used to lubricate moving parts in machines, and can also be used to seal or exclude water and other contaminants.
There are many different types of grease, each with its own properties and uses. The most common types of grease are:
- Automotive grease: This type of grease is designed for use in vehicles. It typically has a high resistance to heat and water, making it ideal for use in bearings and other moving parts that are exposed to the elements.
- Chainsaw grease: This type of grease is designed for use on chainsaws. It is typically heavier than other types of grease, which helps to keep the chain lubricated and running smoothly.
- Food grade grease: This type of grease is designed for use in food processing and preparation. It must meet strict safety standards for food contact and is typically resistant to high temperatures and water.
- Industrial grease: This type of grease is designed for use in industrial applications. It typically has a high resistance to heat, water, and chemicals, making it ideal for use in bearings, valves, and other moving parts that are exposed to harsh environments.
Grease Disposal
Grease disposal should be done in a safe and proper manner to avoid unnecessary accidents and contamination. Used cooking grease can be recycled into biodiesel, so it is important to ensure that it is disposed of correctly. Here are some tips on how to dispose of grease safely:
- Pour the used cooking grease into a heat-resistant container.
- Allow the grease to cool completely before disposing of it.
- Do not pour hot grease down the drain as this can cause clogs.
- Throw the used cooking grease in the trash.
- If you are recycling the used cooking grease, make sure to label the container accordingly.
FAQs
1. What is Type 2 grease?
It is a grease that can withstand oxygen and harsh chemicals in industrial settings. Plain and anti-friction bearings operating at medium speeds and moderate loads benefit greatly from grade 2 grease.
2. What is the difference between number 1 and number 2 grease?
When #1 grease is thinner and slipperier, it is more tractable, while #2 grease is thicker and stiffer, making it ideal for all-purpose applications. While it is widely believed that grease application during the winter is a one-time process, this is not the case.
3. What does 00 mean in grease?
The NLGI Consistency Grade Scale was developed by this institute and assigns numerical ratings based on grease hardness. As a rule of thumb, 000 is very fluid, 00 is semi-fluid, 0 is fluid, 1 is soft, 2 is medium, 3 is medium-hard, 4 is hard, 5 is very hard, and 6 is blocky.
3. What is 0 grease used for?
This high-performance EP lubricant provides protection from vibrations and high loads without compromising its performance. This grease has been designed for trucks and buses equipped with a central lubrication system, particularly engine reductions and gearboxes where NLGI-0 grease is recommended.
4. What is EP mean in grease?
EP grease is formulated with additives to increase its load-carrying capacity under extreme pressure.
5. What is #3 grease?
NLGI 3 refers to the consistency of vegetable shortening. Grease based on synthetic oil performs longer than grease based on mineral oil. It is made with PTFE thickener, so it is heat and moisture-resistant. Gears and chains with high torque and low speed perform best with it.
6. What do grease colors mean?
Grease does not have a specific color, whether it is red, green, blue, or yellow. Manufacturers add color to differentiate their grease products, for marketing purposes.
7. What is FM grease?
In the food and beverage processing and packaging industries, FM Grease 2 is a multipurpose heavy-duty grease lubricant designed specifically for grease lubricating machinery.
8. What is MP3 in grease?
In both automotive and industrial applications, MP3 Grease is an excellent lithium-based NLGI 3 multipurpose grease. It is manufactured from high-quality base stocks, superior-quality lithium soap, and performance additives.
