How about talking about lubricants?

Additives are the essence of modern high-performance lubricants. By selecting and adding them appropriately, it is possible to improve their physicochemical properties, endow the lubricants with new special characteristics, or enhance certain existing properties, thereby meeting higher requirements. Carefully selecting additives, carefully balancing them, and formulating them appropriately based on the required quality and performance of the lubricant is key to ensuring its quality. Commonly used additives include: viscosity index improvers, pour point depressants, antioxidants, detergents and dispersants, friction modifiers, oiliness agents, extreme pressure agents, antifoam agents, metal passivators, emulsifiers, corrosion inhibitors, rust inhibitors, and demulsifiers.

Not quite sure; I’m just sharing some information in an effort to stimulate further discussion. Lubricant: rùnhuáyóu. (1) Oil used as a lubricant, such as distillates of petroleum or fatty oils. (2) An oily liquid applied to the surfaces of moving parts in machines such as bearings. It helps to reduce friction, prevent overheating, and avoid machine wear. It is generally a product of petroleum distillation, and it can also be extracted from vegetable and animal oils. Also known as “grease”. 　　Non-volatile oily lubricant. Based on their origin, they are divided into three categories: animal and vegetable oils, petroleum-based lubricants, and synthetic lubricants. Petroleum-based lubricants account for over 97% of the total usage, so lubricants generally refer to petroleum-based lubricants. It is mainly used to reduce friction between the surfaces of moving parts, and it also serves to cool, seal, prevent corrosion and rust, provide insulation, transmit power, and remove impurities from machinery and equipment. Primarily using lubricating oil fractions and residue fractions from crude oil distillation units as raw materials, processes such as solvent deasphalting, solvent dewaxing, solvent refining, hydrorefining or acid-base refining, and clay refining are employed to remove or reduce components that cause the formation of free carbon, substances with low viscosity indices, materials with poor oxidation stability, paraffins, and chemicals that affect the color of the finished oil. This yields qualified lubricating oil base oils, which, after blending and the addition of additives, become lubricant products. The most important properties of lubricating oil are viscosity, oxidation stability, and lubricity, which are closely related to the composition of its fractions. Viscosity is an important quality indicator that reflects the fluidity of lubricating oil. Different usage conditions require different viscosity levels. Mechanisms that operate under heavy loads and at low speeds require lubricants with high viscosity. Oxidation stability refers to the antioxidant capacity of oils in their operating environment, as influenced by temperature, oxygen in the air, and metal catalysis. After oil oxidation, depending on the operating conditions, fine carbonaceous substances primarily composed of asphaltenes are formed, appearing as sticky pitch-like materials or coatings, or as viscous aqueous substances, thereby reducing or eliminating its performance. Lubricity refers to the anti-friction property of lubricating oil. I. Functions of Lubricants Lubricants are liquid substances used in various types of machinery to reduce friction and protect the machinery as well as the components being processed. Their main functions include lubrication, cooling, rust prevention, cleaning, sealing, and cushioning. Lubricating oils account for 85% of all lubricant materials, with a wide variety of types and grades; the global annual consumption is currently around 38 million tons. The general requirements for lubricating oils are: (1) to reduce friction and wear, thereby lowering frictional resistance to save energy, reducing wear to extend the service life of machinery, and improving economic efficiency ； 　　(2) Cooling: It is necessary to remove the friction heat from the machine at all times ； 　　(3) Sealing: leakage prevention, dust protection, and air leakage prevention are required ； 　　(4) Corrosion and rust resistance, to protect the friction surface from oil degradation or external erosion ； 　　(5) Clean flushing: It is necessary to remove the dirt accumulated on the friction surface ； 　　(6) Stress dispersion buffering, distributing loads and mitigating shocks as well as reducing vibration ； 　　(7) Kinetic energy transfer, hydraulic systems, remote-controlled motors, and frictionless variable speed transmission, etc. II. Composition of lubricating oil Lubricating oil generally consists of two components: base oil and additives. Base oil is the main component of lubricants and determines their basic properties, while additives can compensate for and improve the shortcomings of the base oil’s performance, endowing it with certain new properties; they are an important part of lubricants. 　　1. Lubricant base oils 　　　Lubricant base oils are mainly divided into two categories: mineral base oils and synthetic base oils. Mineral base oils are widely used and account for a large proportion (over 95%), but in some applications products formulated with synthetic base oils are necessary, which has led to the rapid development of synthetic base oils. 　　Mineral base oil is derived from crude oil. The main production processes for lubricant base oils include: atmospheric and vacuum distillation, solvent deasphalting, solvent refining, solvent dewaxing, and clay or hydrogenation-based further refining. In 1995, China’s current standards for lubricant base oils were revised, primarily by changing the classification method, and standards for two specialized types of base oils—those with low freezing points and those that have undergone advanced refining—were added. In the production of mineral-based lubricants, the most important thing is to select the best crude oil. 　　The chemical composition of mineral base oils includes high-boiling-point, high-molecular-weight hydrocarbons and non-hydrocarbon mixtures. Its composition generally includes alkanes (straight-chain, branched, highly branched), cycloalkanes (monocyclic, bicyclic, polycyclic), aromatics (monocyclic aromatics, polycyclic aromatics), cycloalkyl aromatics, as well as oxygen-containing, nitrogen-containing, and sulfur-containing organic compounds, along with non-hydrocarbon compounds such as resins and asphaltenes. 　　2. Additives Additives are the essence of modern high-quality lubricants. By selecting and adding them appropriately, it is possible to improve their physicochemical properties, endow the lubricants with new special characteristics, or enhance certain existing properties, thereby meeting higher requirements. Carefully selecting additives, carefully balancing them, and formulating them appropriately based on the required quality and performance of the lubricant is key to ensuring its quality. Commonly used additives include: viscosity index improvers, pour point depressants, antioxidants, detergents and dispersants, friction modifiers, oiliness agents, extreme pressure agents, antifoam agents, metal passivators, emulsifiers, corrosion inhibitors, rust inhibitors, and demulsifiers. III. Basic Properties of Lubricating Oils Lubricants are technology-intensive products that are mixtures of complex hydrocarbons, and their actual performance in use is the result of a combination of complex physical or chemical processes. The basic properties of lubricating oils include general physical and chemical properties, special physical and chemical properties, and simulation bench tests. 　　General physical and chemical properties Each type of lubricant has its common general physical and chemical properties, which indicate the inherent quality of that product. For lubricating oils, these general physical and chemical properties are as follows: （1） Appearance (colority) The color of the oil often reflects its degree of refinement and stability. For base oils, generally the higher the degree of refining, the more thoroughly the hydrocarbon oxides and sulfides are removed, resulting in a lighter color. However, even under the same refining conditions, the base oils produced from crude oils of different origins and parent species may vary in color and transparency. 　　For new finished lubricating oils, due to the use of additives, color has lost its original significance as an indicator of the degree of refinement of the base oil. 　　　(2) Density Density is the simplest and most commonly used physical property indicator for lubricants. The density of lubricating oil increases as the amounts of carbon, oxygen, and sulfur in its composition increase. Therefore, at the same viscosity or the same relative molecular mass, lubricating oils with a high content of aromatics, as well as those with high levels of gums and asphalts, have the highest density; those with a high content of naphthenes have a medium density, while those with a high content of alkanes have the lowest density. 　　　(3) Viscosity Viscosity reflects the internal friction of an oil and is an indicator of its viscosity and fluidity. Without the addition of any functional additives, the higher the viscosity, the greater the strength of the oil film and the poorer its fluidity. 　　　(4) Viscosity Index The viscosity index indicates the degree to which the viscosity of a oil changes with temperature. The higher the viscosity index, the less the viscosity of the oil is affected by temperature, indicating better viscosity-temperature properties; conversely, the lower the viscosity index, the worse these properties are. 　　　(5) Flash point The flash point is an indicator of the volatility of oils. The lighter the fraction of the oil, the greater its volatility, and the lower its flash point as well. Conversely, the heavier the distillate of the oil, the lower its volatility, and the higher its flash point. At the same time, the flash point is an indicator of the fire hazard of petroleum products. The hazard level of oils is determined based on their flash point: oils with a flash point below 45°C are considered flammable, while those with a flash point above 45°C are considered combustible. It is strictly prohibited to heat oils to their flash point temperature during storage and transportation. At the same viscosity, the higher the flash point, the better. Therefore, when selecting lubricating oil, users should choose based on the operating temperature and the working conditions of the oil. It is generally believed that a flash point 20–30°C higher than the operating temperature ensures safe use. 　　　(6) Freezing point and pour point The freezing point is the highest temperature at which the oil stops flowing under specified cooling conditions. The solidification of oils differs greatly from that of pure compounds. Oil does not have a definite freezing temperature; the so-called “freezing” simply means that it loses its fluidity as a whole, and not all of its components turn into solids. 　　The freezing point of lubricating oil is an important quality indicator that reflects its flowability at low temperatures. It is of great significance for production, transportation, and use. Lubricants with a high freezing point cannot be used at low temperatures. On the contrary, in areas with higher temperatures, there is no need to use lubricants with a low freezing point. Because the lower the freezing point of the lubricating oil, the higher its production cost, resulting in unnecessary waste. Generally speaking, the freezing point of lubricating oil should be 5~7°C lower than the lowest temperature of the operating environment. It is particularly important to note that when selecting a lubricant for low temperatures, comprehensive consideration should be given to the oil’s freezing point, viscosity at low temperatures, and viscosity-temperature characteristics. Because oils with low freezing points may also have low-temperature viscosity and viscosity-temperature properties that do not meet the requirements. 　　Both the freezing point and the pour point are indicators of the low-temperature flowability of oils; there is no fundamental difference between them, only slight variations in the methods of measurement. The freezing point and pour point of the same oil product are not exactly equal; generally, the pour point is 2–3°C higher than the freezing point, though there are exceptions. 　　　(7) Acid value, alkali value, and neutralization value The acid value is an indicator of the acidic substances present in lubricating oil, with the unit being mgKOH/g. The acid value is divided into strong acid value and weak acid value; the sum of the two gives the total acid value (abbreviated as TAN). What we usually refer to as the “acid value” actually means “Total Acid Number (TAN)”. 　　The alkalinity value is an indicator of the content of basic substances in lubricating oil, with the unit being mgKOH/g. 　　Alkalinity is also divided into strong alkalinity and weak alkalinity; the sum of the two constitutes the total alkalinity (abbreviated as TBN). What we usually refer to as “alkalinity” actually means “Total Base Number (TBN)”. 　　The neutralization value actually includes the total acid value and the total base value. However, unless otherwise specified, the so-called \"neutralization value\" generally refers only to the \"total acid value\", which is also expressed in mgKOH/g. 　　　(8) Moisture Moisture refers to the percentage of water contained in the lubricant, usually expressed as a weight percentage. The presence of water in lubricating oil can destroy the oil film formed by the lubricant, reducing its lubricating effect, accelerating the corrosion of metals by organic acids, causing equipment to rust, and leading to the formation of sediment in the oil. In short, the less moisture in the lubricant, the better. 　　　(9) Mechanical impurities Mechanical impurities refer to precipitates or colloidal suspensions present in lubricating oil that are insoluble in solvents such as gasoline, ethanol, and benzene. Most of these impurities are sand, gravel, iron filings, and various organometallic salts that are insoluble in solvents and result from additives. Generally, the mechanical impurities in lubricant base oils are kept below 0.005% (levels below 0.005% are considered to be absent). 　　　(10) Ash and sulfuric ash Ash refers to the non-combustible substances that remain after burning under specified conditions. The composition of ash is generally considered to be various metal elements and their salts. Ash content has different meanings for various types of oils; for base oils or oils without additives, ash content can be used to determine the degree of refinement of the oil. For oils with metal salt additives (new oil), ash content becomes a means to quantitatively control the amount of additives added. Abroad, sulfuric acid ash is used in place of ash. The method is to add a small amount of concentrated sulfuric acid before burning the oil sample and carrying out ashing, so as to convert the metal elements of the additive into sulfates. 　　　(11) Residue The charred black residue formed after the oil is heated, evaporated, and burned under specified experimental conditions is called residue. Residue is an important quality indicator for lubricant base oils; it is a parameter specified to determine the properties of the lubricant and the degree of its refinement. In lubricant base oils, the amount of residue is determined not only by its chemical composition but also by the degree of refining of the oil. The main substances that cause residue to form in lubricants are gums, asphaltenes, and polycyclic aromatic hydrocarbons present in the oil. Under conditions of insufficient air, these substances undergo decomposition and condensation under high heat to form residue carbon. The greater the degree of refining of the oil, the lower its residue value. Generally speaking, the lower the carbon residue value of the base oil, the better. 　　Today, many oils contain additives such as metals, sulfur, phosphorus, and nitrogen, which result in high carbon residue values; as a result, the carbon residue value of oils with additives loses its original meaning in carbon residue testing. Mechanical impurities, moisture, ash, and residue are all quality indicators that reflect the purity of oil products, indicating the degree of refinement of the lubricating base oil. IV. Special Physical and Chemical Properties In addition to the aforementioned general physical and chemical properties, each type of lubricant should also possess special physical and chemical characteristics that reflect its specific application properties. The higher the quality requirements, or the greater the specificity of the oil, the more pronounced its special physical and chemical properties become. The test methods that reflect these special physical and chemical properties are briefly described as follows: (1) Oxidation stability. Oxidation stability indicates the anti-aging performance of lubricants; many industrial lubricants designed for long service life are required to meet this criterion, making it a special property specified for such types of oils. There are many methods for determining the oxidation stability of oils. Basically, a certain amount of oil is oxidized at a specific temperature for a set period of time in the presence of air (or oxygen) and metal catalysts, after which the acid value, changes in viscosity, and the formation of precipitates in the oil are measured. All lubricants have different tendencies toward autoxidation, depending on their chemical composition and the external conditions in which they find themselves. Oxidation occurs over time as it is used, gradually resulting in the formation of aldehydes, ketones, acids, as well as substances such as gums and asphaltenes. Oxidation stability is the property that prevents the formation of these substances that are detrimental to the use of oil products. 　　　(2) Thermal stability Thermal stability refers to a lubricant’s ability to withstand high temperatures; in other words, it is the lubricant’s resistance to thermal decomposition, which is expressed by the thermal decomposition temperature. Requirements for thermal stability have been established for some high-quality anti-wear hydraulic oils, compressor oils, and similar products. The thermal stability of oils depends primarily on the composition of the base oil; many additives with low decomposition temperatures tend to have an adverse effect on the stability of the oils ； Antioxidants also cannot significantly improve the thermal stability of oils. 　　　(3) Oiliness and extreme pressure properties Oiliness arises from the polar substances in lubricants forming a strong physicochemical adsorption film on the metal surfaces at the points of friction, thereby providing resistance to high loads and frictional wear. Extreme pressure properties, on the other hand, result from these polar substances decomposing due to frictional chemical reactions under high temperatures and heavy loads at the metal surfaces in contact; these reactions lead to the formation of a low-melting-point, soft (or plastic) extreme pressure film, which provides protection against impacts as well as high loads and high temperatures. 　　　(4) Corrosion and rusting 　　Oxidation of oils or the effect of additives often leads to corrosion of steel and other non-ferrous metals. In corrosion tests, copper strips are generally placed in oil and left at 100°C for 3 hours, after which the changes in the copper are observed ； The corrosion test involves the formation of rust on the surface of steel under the influence of water and water vapor. To determine the rust resistance, 30 ml of distilled water or artificial seawater is added to 300 ml of test oil, after which a steel rod is placed in it and stirred at 54°C for 24 hours; thereafter, it is checked whether rust has formed on the steel rod. Oils should have resistance to metal corrosion and rust prevention; in industrial lubricant standards, these two properties are usually required to be tested. 　　　(5) Antifoaming property: During operation, lubricants often form foam due to the presence of air. This is especially true when the oil contains surfactant additives, as foam is more likely to form and it is also difficult for such foam to disappear. Foam formation during the use of lubricant can damage the oil film, cause sintering of the friction surfaces or increase wear, accelerate the oxidation and deterioration of the lubricant, and also cause air blockages in the lubrication system, affecting the circulation of the lubricant. Therefore, antifoaming property is an important quality indicator for lubricants and the like. 　　　(6) Hydrolytic stability 　　　Hydrolytic stability indicates the stability of oils under the action of water and metals (mainly copper). When an oil has a high acid value, or contains additives that decompose into acidic substances when exposed to water, this parameter often fails to meet the required standards. The method for determining it involves adding a certain amount of water to the oil sample, mixing it with a copper sheet at a specific temperature for a set period of time, and then measuring the acid value of the water layer as well as the weight loss of the copper sheet. 　　　(7) Emulsion resistance: Industrial lubricants often inevitably become mixed with some cooling water during use. If the lubricant lacks good emulsion resistance, it will form an emulsion with the water that has mixed in, making it difficult to remove the water from the bottom of the circulation tank; this can lead to poor lubrication. Therefore, anti-emulsibility is a very important physicochemical property of industrial lubricants. For ordinary oils, 40 ml of the oil sample is mixed vigorously with 40 ml of distilled water at a certain temperature for a specified period of time, after which the time it takes for the oil layer, water layer, and emulsion layer to separate into 40 ml, 37 ml, and 3 ml respectively is observed ； Industrial gear oil is prepared by mixing the oil with water, stirring at a certain temperature and at 6,000 revolutions per minute for 5 minutes, allowing it to stand for 5 hours, and then measuring the volumes of oil, water, and the emulsion layer. 　　　(8) Air release value: This requirement is specified in the hydraulic oil standards, as in hydraulic systems, if the air dissolved in the oil is not released in a timely manner, it will affect the accuracy and sensitivity of hydraulic transmission; in severe cases, it will fail to meet the requirements for using such hydraulic systems. The method for measuring this property is similar to that for antifoaming, except that it determines the time it takes for the air (mist) dissolved within the oil to be released. 　　　(9) Rubber sealing performance In hydraulic systems, rubber is commonly used as a sealing material. In mechanical devices, oils inevitably come into contact with various sealing elements; oils with poor sealing properties can cause the rubber to swell, shrink, harden, or crack, thereby affecting its sealing ability. Therefore, it is necessary for oils to have good compatibility with rubber. Hydraulic oil standards require a rubber sealing index, which is measured by the change that occurs in a rubber ring of a certain size after being immersed in oil for a specified period of time. 　　　(10) Shear stability: In oils to which thickeners have been added, mechanical shear acts during use, causing the high-molecular polymers in the oil to be broken down, which reduces the viscosity of the oil and interferes with proper lubrication. Therefore, shear stability is a specific physical and chemical property that must be measured for such oils. There are many methods for measuring shear stability, including the ultrasonic shear method, the nozzle shear method, the Wicks pump shear method, and the FZG gearbox shear method; all of these methods ultimately aim to determine the rate of viscosity decrease in the oil. 　　　(11) Solubility 　Solubility is usually expressed by the aniline point. The solubility limit aniline point of composite additives varies with different grades of oils; the limit value for oils with low ash content is higher than that for highly alkaline oils, and the limit value for single-grade oils is higher than that for multi-grade oils. 　　　(12) Volatility 　　　The volatility of the base oil is related to fuel consumption, viscosity stability, and oxidation stability. These properties are particularly important for multi-grade oils and energy-saving oils. 　　　(13) Rust prevention performance This refers specifically to the special physical and chemical properties that rust-proof greases should possess. The testing methods include humidity tests, salt spray tests, laminating tests, and water displacement tests; in addition, there are also greenhouse tests and long-term storage tests. 　　　(14) Electrical properties Electrical properties are unique characteristics of insulating oils, including dielectric loss angle, dielectric constant, breakdown voltage, pulse voltage, etc. The degree of refinement of the base oil, as well as impurities and moisture, all have a significant impact on the electrical properties of the oil. 　　　(15) Special physical and chemical properties of greases In addition to their general physical and chemical properties, greases designed for specific applications possess special physical and chemical properties as well. Greases with good water resistance are required to undergo a water test ； For low-temperature grease, low-temperature torque needs to be measured ； Multi-effect greases need to be tested for extreme pressure and wear resistance as well as rust prevention properties ； Long-life lubricants require bearing life tests and similar procedures. There are also corresponding test methods for measuring these properties. 　　　(16) Other special physical and chemical properties Each type of oil should possess its own unique special properties in addition to its general properties. For example, the cooling rate of quenching oil needs to be determined ； The emulsification stability of the emulsified oil needs to be determined ； The anti-creep coefficient of hydraulic guide rail oil needs to be measured ； The dispersion of oil mist needs to be measured for spray lubricants ； The freezing point and flocculation point of refrigeration oil need to be measured ； Low-temperature gear oil needs to be tested for pitting, etc. All these properties require a special chemical composition of the base oil, or the addition of certain special additives to ensure them. V. Instructions for Using Lubricating Oil Oil storage: 1. It should not be stored upright in an outdoor environment to prevent contamination by moisture and debris. 　　--------- 2. For indoor storage, it can be placed upright with the lid facing up for easy access. 　　--------- 3. Tighten the sealing lid to keep the oil drum sealed. 　　--------- 4. Keep the surface of the barrel clean and the markings clear. 　　--------- 5. Keep the floor clean to facilitate early detection of oil leaks. 　　--------- 6. Keep proper records of inventory entry, with first arrival determining priority. 　　--------- 7. The oil that is drawn frequently is placed on oil drum racks, with the flow of oil being controlled by switches. 　　--------- 8. New oil and used oil should be stored separately; containers that have held used oil must not be used for new oil to prevent contamination. 　　Oil product safety: 1. Oil products should be stored in separate containers, with no flammable materials placed around them. 　　--------- 2. Open flames are strictly prohibited; no kindling is allowed to be brought into the oil depot. 　　--------- 3. Be equipped with no fewer than two fire extinguishers. 　　--------- 4. The rags used for wiping the machinery or the oil residues removed therefrom must not be piled up, to prevent fire propagation. 　　--------- 5. Flammable specialty oils or chemical solvents should be stored separately, with flammable material signs placed on them. 　　Usage notes: 1. Consult a lubrication expert to use lubricants of the appropriate specification, and minimize the number of different types of oil used. 　　--------- 2. Each machine is illustrated with a simple diagram showing the areas that require refueling, the name of the oil to be used, the refueling interval, etc.; ------------a designated person is responsible for this to prevent the use of the wrong type of oil. 　　--------- 3. Clean and wipe containers and tools such as oil pumps and oil pots before each refueling. 　　--------- 4. A separate container for each type of oil, with the name of the oil contained therein indicated on the container to prevent contamination. 　　--------- 5. Before changing the oil, the machinery must be thoroughly rinsed with a solvent; water-soluble cleaners must not be used. 　　--------- 6. Keep proper maintenance records for the machinery after each addition or replacement of lubricant. 　　--------- 7. If any abnormalities are detected in the oil or if it has reached the time for oil change, samples should be taken and sent to a professional company for testing. 　　Environmental protection and health: 1. It is strictly prohibited to discharge used oil directly into sewers or soil to prevent environmental pollution. 　　--------- 2. Used oil and waste liquids should be collected in dedicated containers and then handed over to **licensed recyclers for disposal; they must not be discarded carelessly. 　　--------- 3. People with skin allergies or scratches should avoid direct contact with lubricants. 　　--------- 4. Never wear clothing with oil stains, and do not put oil-contaminated debris into bags. 　　--------- 5. Do not use dirty cloth scraps to wipe away oil from the skin, as metal shavings hidden in those scraps could cause scratches on the skin and lead to infections. 　　Lubricant viscosity chart ISO AGMA SAE Common base oils Viscosity grades Lubricant grades Gears Gearing nomenclature Viscosity grade Viscosity grade VI. Glossary of technical terms Abrasive wear Mechanical wear caused by the relative sliding of two contacting surfaces Additives Small amounts of substances added to improve lubrication properties Adhesion improvers Additives incorporated into oils and greases to enhance adhesion (such as polyisobutylene) Adhesive lubricants Lubricants to which adhesion improvers are added to prevent them from being flung off due to centrifugal force AF coating Anti-friction coating; the most widely used type of dry film solid lubricant, including room-temperature curing and heat-curing types. The formula contains solid lubricant materials (referred to as “raw materials”) and bonding materials; see “Binders”.
Age resistance: The aging of materials caused by oxidation, overheating, or the presence of certain metals (such as copper, lead, silver, etc.). The age resistance of materials can be improved by adding certain additives (such as antioxidants).
ASTM: American Society for Testing and Materials.
Base oil: The fundamental component of lubricants and greases.
Binder: A non-volatile medium or filler used to enhance the strength of the bond between solid lubricant particles or to increase the adhesion between the solid lubricant film and the friction surface.
Bonding lubricant: See AF coating.
Loosening torque: The torque required to loosen a bolted connection.
Chemical inertness: The ability of a lubricant not to react chemically with certain substances.
Friction coefficient: The ratio of the frictional force between two contacting surfaces to the normal force.
Low-temperature performance: For lubricants, this is indicated by cloud point, pour point, and freezing point; for greases, it can be measured using Kesternich flow pressure and low-temperature torque tests.
Colloid: Particles (with particle sizes ranging from 10-5 to 10-7 cm) in a stable liquid, existing as a solute without any particle sedimentation.
Composite grease: A grease made from metal soaps and thickeners derived from various acids, particularly suitable for high-temperature and long-term use.
Consistency: An indicator of greases, expressed as unworked cone penetration and worked cone penetration, and is determined according to NLGI (National Lubricant Grease Institute) standards. The consistency is simply divided into nine grades, for example:
Consistency Grade – Working Cone Penetration (1/10 mm)
00: 400–430
0: 350–385
1: 310–340
2: 265–295

Density – The mass of the lubricant per unit volume at 20°C (g/cm3)

Detergent – A surfactant that removes residual substances and deposits from surfaces.

Dispersibility – The ability to improve the dispersion of insoluble substances in a liquid.

DN Value – A reference value for the rotational speed of rolling bearing grease, expressed as the bearing’s inner diameter (mm) multiplied by the number of revolutions per minute.

Drop Point – The temperature at which the grease changes from a semi-solid state to a liquid state; it is an indicator of the grease’s heat resistance. The drop point is determined as the temperature at which the first drop of liquid falls out of the container as the temperature rises.

Dynamic Viscosity – Also known as absolute viscosity; it reflects the internal resistance between fluid molecules as the lubricant flows. Measured by the flow of lubricant through tube holes or gaps.
EP additive: A chemical substance used to improve resistance to heavy loads and high temperatures, thereby enhancing the wear resistance of oils and greases.
Emcor: A corrosion resistance test for water-based rolling bearing greases; the test involves running at least two bearings lubricated with this grease in water for about a week, with the corrosion resistance score ranging from 0 to 5 (0 indicating no corrosion, 5 indicating severe corrosion).
Ester oil: A compound of acids and alcohols, used as a lubricant material and in the production of greases.
Flash point: The lowest temperature at which a flame is generated when introduced into a mixture of oil vapor and air.
Fluorosilicone oil: Silicone oil containing fluorine atoms in its molecules.
Fretting corrosion wear: A type of mechanochemical wear that occurs due to slight relative sliding between two contacting surfaces; it results in pitting on the friction surfaces and the accumulation of oxidation debris between them.
Friction: The tangential resistance that exists at the contact surface between two objects moving relative to each other.
Grease: A lubricating medium composed of base oil and thickeners.
Inhibitors: Additives used in lubricants to delay aging and corrosion.
Freezing point: The highest temperature at which the oil sample no longer moves when cooled under specified test conditions. Expressed in °C. Pour point: the lowest temperature at which a sample of oil can still flow under specified test conditions. Expressed in °C. It is a standard indicator used to measure the low-temperature flowability of lubricants. For the same type of oil, its pour point is a few degrees higher than its freezing point; in the past the freezing point was commonly used, but nowadays the pour point is the internationally accepted value.