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Basic properties of lubricating oils: Lubricating oils 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 bench test simulations. 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: appearance (colority), which refers to the color of the oil and can often indicate 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 base stocks may vary in color and transparency. For new finished lubricants, due to the use of additives, color has lost its original significance as an indicator of the degree of refinement of the base oil. 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. Viscosity reflects the internal friction of 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. 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; otherwise, the properties are worse. 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 lubricants, users should make their choice based on the operating temperature and working conditions of the lubricant. It is generally believed that a flash point 20–30°C higher than the operating temperature ensures safe use. Freezing point and pour point: The freezing point refers to the highest temperature at which the oil stops flowing under specified cooling conditions. The solidification of oils differs significantly from that of pure compounds. Oils do not have a definite freezing temperature; the so-called “freezing” simply means that the oil as a whole loses its fluidity, but 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 usage. 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, the freezing point of lubricating oil should be 5–7°C lower than the lowest temperature of the operating environment. However, it is particularly worth mentioning that when selecting low-temperature lubricants, one should consider comprehensively the oil’s pour point, low-temperature viscosity, 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. Acid number, alkali number, and neutralization value: The acid number is an indicator of the acidic substances present in lubricating oils, with the unit being mgKOH/g. The acid value is divided into strong acid value and weak acid value; the sum of the two constitutes 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. There are two types of alkalinity values: strong alkalinity value and weak alkalinity value. The sum of these two is the total alkalinity value (abbreviated as TBN). What we usually refer to as “alkalinity value” actually means “total alkalinity value (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. Moisture refers to the percentage of water contained in lubricating oil, 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 efficiency, 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. Mechanical impurities refer to precipitates or colloidal suspensions present in lubricating oils that are insoluble in solvents such as gasoline, ethanol, and benzene. Most of these impurities are things like sand, gravel, and iron filings, as well as some organic metal salts that are poorly soluble 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). 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 oil products with metal salt additives (new oil), ash becomes a means of quantitatively controlling 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 then carrying out ashing, so as to convert the metal elements of the additive into sulfates. Under specified experimental conditions, the charred black residue formed after the evaporation and combustion of residual carbonaceous oils is known as 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 formation in lubricants are gums, asphaltenes, and polycyclic aromatic hydrocarbons present in the oil. Under conditions of insufficient air, these substances undergo decomposition and condensation due to intense heat, resulting in the formation of 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. In addition to the aforementioned general physical and chemical properties, each type of lubricant should also possess specific physical and chemical characteristics that reflect its operational properties. The higher the quality requirements or the greater the specificity of an oil, the more prominent its special physical and chemical properties become. The test methods for reflecting these special physicochemical properties are briefly introduced as follows: Oxidation stability indicates the anti-aging performance of lubricants. Some industrial lubricants with a long service life are required to meet this criterion, making it a special property specified for such types of lubricants. 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 producing substances such as aldehydes, ketones, acids, as well 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. Thermal stability refers to a lubricant’s ability to withstand high temperatures; it is the lubricant’s resistance to thermal decomposition, which is expressed in terms of 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. Oiliness and extreme pressure properties work by 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 property, on the other hand, involves these polar substances decomposing due to frictional chemical reactions caused by high temperatures and heavy loads at the metal surfaces in contact with each other; this leads to the formation of a low-melting-point, soft (or plastic) extreme pressure film that provides protection against impacts as well as high loads and high temperatures. Corrosion and rusting often result from the oxidation of oils or the action of additives, causing damage to steel and other non-ferrous metals. In corrosion testing, a copper strip is usually 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, a steel rod is placed in this mixture, and it is stirred at 54°C for 24 hours; thereafter, it is checked whether rust has formed on the steel rod. The oil should have anti-metallic corrosion and anti-rust properties. In industrial lubricant standards, these two parameters are usually mandatory test items. During operation, anti-foaming lubricating oils often generate foam due to the presence of air. This is especially true when the oil contains surface-active additives; under such circumstances, foam forms more readily and is also difficult to dissipate. Foam generated during the use of lubricating oil can damage the oil film, leading to scuffing or increased wear on the friction surfaces. It also promotes the oxidation and degradation of the lubricating oil. Additionally, it can cause air blockage in the lubrication system, thereby affecting the circulation of the lubricating oil. Therefore, anti-foaming properties are an important quality indicator for lubricating oils, etc. Hydrolytic stability: This parameter evaluates the stability of oils under the influence of water and metals, particularly copper. An oil with a high acid value, or one that contains additives that decompose into acidic substances when exposed to water, will often fail this test. Its determination method involves adding the test oil to a certain amount of water, mixing and stirring it with a copper sheet at a specified temperature for a certain period of time, and then measuring the acid value of the water layer and the weight loss of the copper sheet. Industrial lubricants with poor emulsification resistance often inevitably become mixed with some cooling water during use. If such lubricants lack sufficient emulsification resistance, they will form an emulsion with the water that has mixed in, making it difficult to remove the water from the bottom of the oil tank – which 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 40-37-3 ml 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. This requirement is specified in the hydraulic oil standards for air release values, 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 capacity, except that it measures the time it takes for the air (mist) dissolved within the oil to be released. In hydraulic systems, rubber is commonly used as a sealing material. In mechanical devices, oils inevitably come into contact with various sealing components; oils that do not have good compatibility with rubber can cause the rubber to swell, shrink, harden, or crack, thereby affecting its sealing performance. 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. In oils to which shear stability agents and viscosity enhancers have been added, mechanical shear during use breaks down the high-molecular polymers present in the oil, resulting in a decrease in its viscosity and thereby affecting 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. 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 basic oils, and the limit value for single-grade oils is higher than that for multi-grade oils. The volatility of volatile base oils is related to fuel consumption, viscosity stability, and oxidation stability. These properties are particularly important for multi-grade oils and energy-saving oils. Rust resistance refers specifically to the special physical and chemical properties that rust-proof greases should possess. The testing methods for this include humidity tests, salt spray tests, laminate tests, and water displacement tests; in addition, there are also greenhouse tests and long-term storage tests. Electrical properties are unique characteristics of insulating oil, including the 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. Special physicochemical properties of grease: In addition to their general physicochemical properties, greases designed for specific applications possess special physicochemical characteristics. 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 the like. There are also corresponding test methods for measuring these properties. Other special physical and chemical properties: In addition to their general properties, each type of oil should have its own unique special 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 from the sprayed lubricant needs to be measured ； 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. Instructions for using lubricating oil: Storage of the oil: 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 ensure the markings are clear. 5. Keep the floor clean to facilitate early detection of oil leaks. 6. Keep proper records of inventory entry, with first arrival, first served. 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 in the oil depot. 3. 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 try to minimize the number of different types of oil used. 2. Each type of machinery is illustrated with simple diagrams showing the areas that require refueling, the name of the oil to be used, and the refueling interval; a designated person is responsible for ensuring that the correct oil is used. 3. Clean and wipe containers and tools such as oil pumps and oil cans 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. Environment 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 dumped 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 oil from the skin, as metal shavings hidden in those scraps could scratch the skin and cause infections. Glossary of technical terms: Abrasive wear: Mechanical wear that occurs as a result of 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 in order to prevent them from being flung off due to centrifugal forces. AF coatings, anti-friction coatings: The most widely used dry film solid lubricants, including those that cure at room temperature and those that require heat curing. The formula contains solid lubricant materials (referred to as “raw materials”) and bonding materials; see “Binders”. Aging resistance: The aging of materials caused by oxidation, overheating, or the presence of certain metals (such as copper, lead, silver, etc.) 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. Binders: Non-volatile substances or agents used to enhance the strength of the bonds between solid lubricant particles or to improve the adhesion between the solid lubricant film and the friction surface. Loosening torque: The torque required to loosen a bolt connection. Chemical inertness: The ability of a lubricant not to react chemically with certain substances. Coefficient of friction: 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. Colloids: Particles in a stable liquid (with particle sizes ranging from 10-5 to 10-7 cm) that exist as a solution without any particle sedimentation. Composite greases: Greases made using 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, expressed in g/cm3. Cleaners: Surfactants that remove residual substances and precipitates from the surface. Dispersibility: The ability to disperse insoluble substances in a liquid. DN value: A reference value for rolling bearing grease based on rotational speed, calculated by multiplying the bearing’s inner diameter in mm by the number of revolutions per minute. Dropping 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. As the temperature rises, the dropping point is defined as the temperature at which the first drop of liquid falls out of the container. Dynamic viscosity: Also known as absolute viscosity, it reflects the internal resistance between fluid molecules as the lubricant flows. Determining EP additives by observing the flow of lubricant through pores or gaps: 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 rolling bearing greases in water, conducted by running at least two bearings lubricated with this grease in water for about a week; the corrosion resistance value ranges from 0 to 5 (0 indicating no corrosion, 5 indicating severe corrosion). Ester oils: Compounds of acids and alcohols, used as lubricants and in the production of greases. Flash point: The lowest temperature at which a flame ignites when introduced into a mixture of oil vapor and air. Fluorosilicone oils: Silicone oils containing fluorine atoms in their molecules. Fretting wear: A type of mechanochemical wear that occurs due to slight relative sliding between two contacting surfaces, resulting in pitting on the friction surface and the accumulation of oxidized debris between those surfaces. Friction: The tangential resistance that exists at the contact interface between two objects moving relative to each other. Greases: Lubricating substances composed of base oils 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. The pour point is expressed in °C: the lowest temperature at which a cooled sample of the oil can still flow under specified test conditions. Expressed in °C. It is a standard indicator used to measure the low-temperature flowability of lubricating oils. 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. Looking ahead to the next 10 years, the demand for lubricants in the Asia-Pacific region is set to reach 15.5 million tons, with China accounting for 40% of that demand. By 2020, the demand for lubricants in the Chinese market is set to double, with consumption likely to exceed that of the United States. The rapid growth in domestic demand for vehicle fuels, along with the trend toward higher-quality fuels, will drive the vehicle lubricant industry into a period of rapid development. As the demand for lubricants for vehicles increases year by year, the quality levels of these lubricants will also see rapid development, with high-quality products becoming directly aligned with international standards. Does a high viscosity of lubricant indicate good quality? Generally, when the operating speed of components is high, the load on their surfaces is lower, so the viscosity of the lubricant required for use is lower (e.g., spindle oil); conversely, the viscosity of the lubricant needed is higher (e.g., gear oil). Of course, it is essential to follow the guidelines provided by the equipment manufacturer regarding the choice of lubricant. In addition to viscosity, there are many other criteria that determine the quality of a lubricant, so viscosity alone cannot be used to assess its quality. Lubricating oils are generally products of petroleum distillation, and some are also extracted from animal and vegetable oils. Also known as “grease”. Non-volatile oily lubricant. Based on their source, they are divided into three categories: animal and vegetable oils, petroleum lubricants, and synthetic lubricants. Petroleum-based lubricants account for over 97% of the total usage, so lubricants usually 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 parameter 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 anti-oxidation 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 performance of lubricating oil. The function of lubricating oil: Lubricating oil is a liquid lubricant used in various types of machinery to reduce friction and protect the machinery as well as the components being processed. Its 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 overall requirements for lubricants are: (1) to reduce friction and wear, thereby lowering frictional resistance to save energy, reducing wear to extend the lifespan of machinery, and improving economic efficiency ； (2) Cooling: It is necessary to remove the friction heat from the machine at all times ； (3) Sealing: must be leak-proof, dust-proof, and airtight ； (4) Corrosion and rust resistance, to protect the friction surface from oil degradation or external erosion ； (5) Clean rinsing: 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. Lubricant composition: Lubricants generally consist of two parts: 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. Lubricating oil in barrels and canned form should, where possible, be stored in a warehouse to protect it from weather conditions; lubricating oil that has already been opened must also be stored in a warehouse. Oil drums should be placed in a horizontal position, with wooden wedges used at both ends to prevent them from rolling. In addition, the oil tank should be regularly checked for leaks and to ensure that the markings on its surface are clear. If it is necessary to place the barrel upright, it is advisable to turn it upside down with the lid facing downward, or to tilt it slightly, so as to prevent rainwater from accumulating on the surface of the barrel and covering the latch. Water has a negative effect on any lubricant. On the surface, it seems difficult for moisture to penetrate through a sealed barrel lid and enter the oil barrel. However, oil barrels stored outdoors are exposed to the scorching sun during the day and cooler temperatures at night; this expansion and contraction due to temperature changes affects the pressure of the air inside the barrel ； It is slightly above atmospheric pressure during the day, and approaches a vacuum at night. This change in pressure between day and night creates a \"breathing\" effect: during the day, some air is \"exhaled\" from the barrel, while at night air is \"inhaled\" into it. If the barrel lid is submerged in water, then moisture will inevitably enter the barrel along with the air at night. Over time, the amount of water mixed in with the oil can become quite significant. When extracting oil, the oil barrel should be placed horizontally on a wooden frame at an appropriate height. A faucet should be installed at the opening of the barrel for draining the oil, and a container should be placed under the faucet to prevent drips. Alternatively, place the oil barrel upright, insert the oil pipe into the barrel’s lid opening, and draw oil using a hand pump. When bulk oil is stored in tanks, it is inevitable that condensation water and contaminants will mix in, eventually accumulating at the bottom of the tank to form a sludge-like substance that contaminates the lubricating oil. Therefore, the bottom of the tank should be designed in a funnel-shaped or inclined pattern, and an exhaust plug should be installed to allow the residue to be removed on schedule. To the extent possible, the interior of the oil tank should be cleaned regularly. Temperature has a greater impact on grease than on lubricating oil; prolonged exposure to high temperatures (such as sunlight) can cause the oil components in the grease to separate. Therefore, grease containers should be stored in a warehouse, with the opening facing upward. The opening of the bucket used to hold grease is large, allowing dirt and water to penetrate more easily; the lid should be closed tightly immediately after use. Temperatures that are too low or too high have an adverse effect on lubricants; therefore, it is not advisable to store lubricants in places that are either too cold or too hot for extended periods of time. 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 (linear, branched, highly branched), cycloalkanes (monocyclic, bicyclic, polycyclic), aromatics (monocyclic aromatics, polycyclic aromatics), cycloaliphatic aromatics, as well as oxygen-containing, nitrogen-containing, and sulfur-containing organic compounds, along with non-hydrocarbon compounds such as resins and asphaltenes. In the past, major foreign oil companies classified base oils into paraffinic base oils, intermediate base oils, naphthenic base oils, etc., based on the properties of crude oil and the processing methods used. Since the 1980s, driven by the development of engine oils, lubricants have tended to be lower in viscosity, more multi-grade, and more universal in use, which has led to higher requirements for the viscosity index of base oils. The previous classification methods for base oils can no longer accommodate this trend. Therefore, major foreign oil companies currently generally classify based on the viscosity index, but there has been no strict standard to date. In 1993, API classified base oils into five categories (API-1509) and incorporated them into the EOLCS (API Engine Oil Certification System).