1.Density and relative density

    Density is the mass number of a substance per unit volume, expressed in g/cm3 or g/mL, at a given temperature. Relative density refers to the ratio of the density of positive gas at a given temperature to the density of a standard substance at a given temperature. The standard substance for petroleum liquids is water.


        A measure of the internal friction force of a fluid flow is called viscosity, which decreases with increasing temperature. Most lubricants are graded according to their viscosity. Viscosity is generally expressed in five ways, namely, dynamic viscosity, kinematic viscosity, Engler's viscosity, Reye's viscosity and Sayer's viscosity.
       Dynamic viscosity: a measure of the internal friction force of a fluid flowing under a certain shear stress. Its value is the ratio of shear stress and shear rate added to the fluid. In Chinese legal units of measurement, it is in Pa•s. It is customary to use Cp as the unit, 1CP = 10-3pA •s.
       Kinematic viscosity: a measure of the internal friction force of a liquid flowing under the action of gravity. Its value is the ratio of the dynamic viscosity of a liquid to its density at the same temperature. In China, the unit of legal measurement is m2/s. It's customary to use CST,1cst=1mm2/s.
        Engler viscosity: the ratio of the time (s) required for a sample of a given volume to flow out of the hole of the engler viscometer for 200mL of test increment under specified conditions to the value of the water measured by the viscometer, expressed as 0Et.
       Redwood viscosity: the amount of time, in s, required for a sample of a given volume to flow out of a 50mL specimen from the redwood viscometer under specified conditions.
        Saybolt viscosity: The time, in s, required for a sample of a given volume to flow out of the Saybolt viscometer under specified conditions. Sayable viscosity is divided into Sayable universal viscosity (expressed as SUV) and Sayable heavy oil viscosity (expressed as SFV).

    3.Viscosity index

      The viscosity index is a conventional measure of the properties of oil viscosity with temperature. A high viscosity index indicates that the viscosity of an oil varies little with temperature and vice versa.

    4.Flash point

    Under specified conditions, the minimum temperature at which a mixture of steam and air escaping from the heated oil comes into contact with the flame for an instant of fire is called the flash point, expressed in degrees Celsius. The method of measuring flash point is divided into open-mouth cup method and closed-mouth cup method. The open-mouth cup method is used to measure the flash point of heavy lubricant. The close-mouth cup method is used to determine the flash point of fuel and light lubricants.

    5.Freezing point

       The maximum temperature when the oil is cooled to stop moving under the specified conditions is called the freezing point and is expressed as ℃. Freezing point is an item to evaluate the low temperature performance of oil products.
       The condensation point of oil has a direct relationship with wax content, the more wax content in oil, the higher the condensation point. Therefore, the condensation point can guide the dewaxing process operation in the petroleum product processing technology.

    6.Pour point

       Pour point refers to the lowest temperature at which the cooled test oil can flow under specified conditions, expressed as ℃. Pour point and condensation point are used to represent the low temperature flow performance of petroleum products.


       Moisture is the amount of water in the oil, expressed as a percentage by weight. There are several moisture determination methods in the petroleum product analysis standard, generally expressed in %, less than 0.03% is the trace. A specially required oil whose moisture content is expressed in terms of 10-6 (PPM).

    8.Mechanical impurities

       All impurities present in the oil that do not dissolve in the specified solvent are called mechanical impurities.

    9.Water soluble acid or base

       Water soluble acid or base refers to the existence of water soluble acid or alkaline substances in oil products.

    10.Carbon residue

       Under specified conditions, the residue formed in the pyrolysis of oil products is called carbon residue. Expressed as a percentage by weight.


       The inorganic substance obtained by calcining the residue of the oil after being carbonized under specified conditions is called ash and is expressed as a percentage by weight. The ash is mainly naphthenate, which is found in oils. Usually the ash content of oil products is very small. When some high ash additives are added to lubricating oil, the ash content of oil products will increase.

    12.Break emulsion value

       The measurement of the separation ability of oil products from oil-water emulsion is called demulsification value, which is expressed in min. It is one of the main specifications of turbine oils. Turbine oil in the process of use, sometimes with water leakage, leakage contact, or even mixed, the formation of temporary emulsification, so it must be able to quickly separate the performance of water, in order to ensure the normal circulation of oil and lubrication parts.

    13.Oxidation stability

      The ability of a petroleum product to resist the action of air (or oxygen) without permanently changing its properties is called the oxidation stability of the product.

    14.Shear stability

       Shear stability refers to the ability of a petroleum product to resist shear action and maintain viscosity viscosition-related properties under specified conditions.

    15.Ditching point

       The trenching point is to store the test oil samples at a specified temperature for 18h, cut the test oil into a trench with a metal sheet, and then determine whether the test oil flows together within 10s and cover the bottom of the test oil container. If the oil sample flows back within 10s and completely covers the bottom of the oil test container, the report shows that the oil sample is not gully. On the other hand, report oil sample groove. Trenching point is to determine the trenching performance of gear oil at low temperature.

    16.Drop point

       The minimum temperature at which a solid or semi-solid petroleum product reaches a certain fluidity under specified conditions is called the drop point, expressed in degrees Centigrade. The drop point of a grease has a great deal to do with its composition. The general range of drop points of commonly used grease is as follows:

    Range of drop points of commonly used grease

    Name of grease

    Drop point 

    SG-4 Silicone grease 





















       At 25℃, the depth at which a standard cone with a total load of 150±0.25g penetrates vertically into the grease sample within 5s is called the grease coning degree, expressed as 1/10mm.

    18.Free acids and free bases

       Grease is plant and animal oil or whole fatty acid after alkali saponification, thickening mineral oil and become. If the saponification is incomplete or the mineral oil is oxidized and decomposed, free acids will appear. If too much base is used, free base will appear at the high tip. The presence of too many free acids and bases will cause corrosion of parts, so the free acids and bases of grease should be controlled within a certain value.

    19.Colloidal stability

      Grease in use or long-term storage will have a small amount of oil precipitation, this phenomenon is called oil separation. The resistance of a grease to oil separation is called colloidal stability.

    20.Mechanical stability

       The mechanical stability of a grease, also known as shear stability, indicates the resistance of the grease to changes in consistency under mechanical working conditions. Under the long-term action of mechanical force, the consistency of the grease will decrease. Under extremely harsh conditions, the structure of the grease will be destroyed and become a fluid, which will be lost from the lubricating part and lose its lubricating effect. This is because the thickening agent fiber structure, when subjected to a long time of shear damage, the fiber becomes shorter, resulting in a decrease in consistency, in the light of the shear, the fiber can be recombined to restore the consistency, this mechanical shear performance, known as the mechanical stability of grease.

    Q: What is the code name for lubricating base oil?

      A: According to the sinopec lubricating base oils Classification [Q/ shr001-95 (99)], the code names of lubricating base oils are determined according to the viscosity index and the applicable scope. Each breed is represented by a group of English letters.

    1、The code name for a lubricating base oil is composed of letters indicating the viscosity index. UH", "VH", "H", "M", "L" are the prefix for "Ultra High", "Very High", "High", "Middle", "Low". Not only for Viscosity Index, but also for Viscosity Index.

    2、The code name of lubricating oil special base oil is composed of the code name and special symbol of lubricating oil general base oil. , the special symbol is an English letter representing the characteristics of the base oil. "W "is the English prefix of "Winter", indicating its low setting characteristic, and "S" is the English prefix of "Super", indicating its deep refining characteristic.

    3.UHVI, VHVI, HVI, MVI, LVI, UHVIW, VHVIW, HVIW, MVIW, Deep refining UHVIS, VHVIS, HVIS, HVIS, MVIS, High viscosity index (HVI), high viscosity index (VHVI), ultra-high viscosity index (UHVI), and ultra-high viscosity index (UHVI). According to the scope of use, the base oil is divided into general base oil and special base oil

    Q: What are the important indicators of lubricating oil?

    A: 1.Color, often can reflect its refined degree and stability. For base oils, the more refined they are, the cleaner the hydrocarbon oxides and sulfides are removed, and the lighter the color. However, the color and transparency of base oils produced from different sources and base oils may vary even under the same refining conditions. For new finished lubricants, due to the use of additives, color has lost its original meaning as an indicator to judge the refinement degree of base oil.

    2. Density  Density is the simplest and most commonly used physical property index of lubricating oil. The density of the lubricating oil increases with the increase of the amount of carbon, oxygen and sulfur in its composition. Therefore, under the same viscosity or the same relative molecular weight, the lubricating oil with more aromatics and more colloid and asphaltenes has the highest density, the one with more cycloalkanes is in the middle, and the one with more alkanes is the least.

    3. Viscosity  The viscosity reflects the internal friction of oil and is an index of oil's oiliness and fluidity. Without any functional additives, the higher the viscosity, the higher the oil film strength, the worse the fluidity. Viscosity index The degree to which the viscosity of an oil changes with temperature. The higher the viscosity index is, the less the viscosity is affected by temperature, the better the viscosity-temperature property is, and vice versa.

    4. Flash point  Flash point is an indicator of the evaporability of oil. The lighter the fraction, the greater the evaporability and the lower the flash point. On the contrary, the heavier the fraction of oil, the less evaporation and the higher the flash point. At the same time, flash point is the index of ignition risk of petroleum products. The danger level of oil products is divided according to the flash point. The flash point below 45℃ is flammable and the above 45℃ is combustible. It is forbidden to heat oil products to its flash point temperature during the storage and transportation of oil products. With the same viscosity, the higher the flash point, the better. Therefore, users should choose lubricants according to the use of temperature and working conditions of lubricants. It is generally believed that the flash point is 20 ~ 30℃ higher than the use temperature, it can be used safely.

    5.Freezing point refers to the highest temperature at which oil stops flowing under specified cooling conditions. The solidification of an oil product is quite different from that of a pure compound. There is no definite solidification temperature for oil products. The so-called "solidification" only loses its fluidity as a whole, and not all components become solid.  The freezing point of lubricating oil is an important quality index to indicate the fluidity of lubricating oil at low temperature. It is important for production, transportation and use. Lubricating oils with high freezing points cannot be used at low temperatures. In contrast, low freezing lubricants are not necessary in areas with higher temperatures. Because the lower the freezing point of lubricating oil, the higher the production cost, causing unnecessary waste. Generally speaking, the freezing point of lubricating oil should be 5~7℃ lower than the lowest temperature of the service environment. But especially to mention, in the selection of low-temperature lubricants, should be combined with the freezing point of oil, low-temperature viscosity and viscose-temperature characteristics of a comprehensive consideration. Because of the low freezing point of oil, its low temperature viscosity and viscosity-temperature characteristics may not meet the requirements.  Both the freezing point and pouring point are the indicators of low temperature fluidity of oil products. The difference between them is unprincipled, but the measurement method is slightly different. The condensate point and pour point of the same oil product are not exactly the same, generally pour point is higher than the condensate point 2 ~ 3℃, but there are exceptions.