In recent years, with the introduction of international automobile production technology, the rapid development of domestic car industry, the continuous development of China's national economy, the improvement of personal consumption ability, the acceleration of cars into families, and the rapid development of car ownership in China. The rapid development of car ownership directly brings about the problem of environmental pollution. The analysis of environmental monitoring data shows that among these pollutants, except soot and sulfur dioxide, automobile exhaust emission has become an important pollution source of urban air pollution, and because motor vehicles emit at low altitude, it is more harmful to the low altitude atmospheric environment and human body countries all over the world pay more and more attention to energy and environmental pollution. European and American countries, including China, have increasingly strict requirements on automobile exhaust emission indicators. It is urgent to solve the problems of internal combustion engine energy saving, improving automobile fuel economy and controlling automobile exhaust emission. On the one hand, internal combustion engine manufacturers improve the energy saving and emission of the engine by improving the structure of the engine, such as adopting turbocharging technology, electronically controlled common rail high-pressure injection, electronically controlled exhaust gas recirculation, electronic fuel injection system, installing exhaust three-way catalytic converter and other measures to comprehensively improve the power performance of the engine Economy and emission indicators. On the other hand, the structural changes of the engine have more stringent requirements for lubricating oil, and the engine lubricating oil products are required to meet higher fuel economic performance (i.e. energy-saving requirements) the proportion of low viscosity and energy-saving engine oil is increasing. Using low viscosity and energy-saving engine oil to reduce engine friction loss and improve power has become one of the effective ways to improve automobile fuel economy I. Research Status of antifriction agents antifriction agents usually added to energy-saving gasoline engine oil are metal organic compounds and ashless organic compounds (excluding metal elements). Among them, metal organic compounds mainly include molybdenum containing and copper containing organic compounds. The research on the action mechanism of this kind of antifriction agent is not very clear. There are basically the following inferences: molybdenum diffuses into the rough surface, forms a polymer film, forms molybdenum disulfide in situ (most recognized assumptions), and the selective migration of metal (copper) leads to the formation of sparse and easy to shear metal film. Ashless organic compounds include carboxylic acids and their derivatives, amides, imides, amines and their derivatives, phosphorus and phosphoric acid derivatives, organic polymers and borate esters. Due to different action modes, the antifriction mechanism of these compounds is also different. It mainly involves the formation of reaction layer (phosphide and sulfide), adsorption layer and in-situ polymer. Antifriction agent plays an important role in boundary lubrication and mixed lubrication. Among them, ash free organic compounds are the most effective in the mixed lubrication state, while metal organic compounds have a significant effect in the boundary lubrication state II. Application of organic molybdenum antifriction agent it can be learned from the literature in recent years that organic molybdenum compounds are metal organic compounds widely used in gasoline engine oil. These compounds mainly include molybdenum dithiocarbamate (modtc), molybdenum dithiophosphate (MoDTP), molybdenum mixture (molyvan855), etc. In 1968, Eugene v. Rowan of R.T. Vanderbilt company invented the oil-soluble organic molybdenum lubricating oil additive molybdenum dialkyl dithiophosphate as the additive of automobile engine lubricating oil. The additive can reduce the fuel consumption ratio of automobile and prolong the service life of engine. In 1974, J. froeschman et al. Developed molybdenum dialkyl dithiocarbamate lubricating oil additive. Different from molybdenum dialkyl dithiocarbamate, this kind of additive is a powder solid, and its molecules do not contain phosphorus, so as to avoid the possible pollution of phosphorus to the catalyst of tail gas processor. In 1993, researchers of R.T. Vanderbilt company] developed molybdenum mixture. In 1999, researchers of Exxon research and engineering company developed a new organic molybdenum lubricating oil additive, mo3sx (L) 4, (x = 4 ~ 10, l = dialkyl dithiocarbamate). It is said that the compound has good antifriction and anti-wear properties. Infineum immediately prepared high-grade lubricating oil with the additive. After adding organic molybdenum compounds into the lubricating oil, ethyl company passed the Ⅲ e engine program. The results showed that the content of organic molybdenum was 115 & mdash; The tribological performance of 458 mg / L engine oil is better than that of molybdenum free lubricating oil. The energy-saving lubricating oil developed by dongran Co., Ltd. of Japan contains certain molybdenum dialkyl dithiocarbamate additives. Organic molybdenum lubricating oil additive is also added to the advanced lubricating oil prepared by American asland company. The lubricating oil shows good anti-wear performance and can save fuel by 3.4%. SRV test was used to evaluate the effect of the combination of modtc and other additives on the friction coefficient. The test results show that modtc can significantly reduce the friction coefficient at high temperature, and the combination of modtc with ZDDP and dispersant has obvious effect studies have shown that organic molybdenum antifriction agent and ester antifriction agent have synergistic effect in improving the antifriction performance of oil products. There are mainly two kinds of ester antifriction agents: one is organic borate and its borate derivatives; The other is a long-chain organic ester containing only carbon, hydrogen and oxygen. Organic Borates were added to lubricating oil as antioxidants in the early stage, and later studies found that they have good antifriction and antiwear effects. In recent ten years, a large number of borate ester compounds have been reported in U.S. patents, which have certain antifriction and antiwear effects. Boric acid ester reacts with organic amine to produce friction modifier with higher performance than boric acid ester; In addition, by grafting imidazoline and amidation? The boric acid esters also showed better antifriction and antiwear effect. Long chain organic ester compound and organic molybdenum antifriction agent showed a very good synergistic effect in improving friction properties. Long chain ester antifriction agents have obvious antifriction effect in a wide temperature range (40 ℃ - 140 ℃), but the effect is the best in the low temperature area (less than 90 ℃), desorption will occur in the high temperature area, and there will be competition adsorption with other active additives, which will affect the antifriction effect. Organic molybdenum antifriction agent has antifriction effect only in high temperature area (greater than 120 ℃). The antifriction agent system composed of organic molybdenum salt and ester compound is used in American patents III. application of nano lubricating oil additives the application of nanoparticles in lubricating system is a new research field. Nanoparticles have the characteristics of large surface area, high diffusion, easy sintering, reduced melting point and increased hardness. They can not only form a layer of easy shear film on the friction surface and reduce the friction coefficient, but also fill and repair the friction surface to a certain extent. Using nanoparticles as lubricating oil additives can fill and repair the concave convex surface of the friction surface, reduce the surface roughness, increase the actual contact area and reduce the friction. The size of nanoparticles is small and can be considered as approximate spherical. They can roll freely like pebbles on the friction surface, play the role of micro bearing, polish and strengthen the friction surface, support the load, improve the bearing capacity and reduce the friction coefficient. In addition, nanoparticles have high diffusion ability and self diffusion ability, and it is easy to form a penetration layer or diffusion layer with excellent wear resistance on the metal surface, showing the principle of in-situ tribochemistry. There have been many studies on adding nanoparticles into lubricating oil as additives or using organic matter to modify the surface of nanoparticles as antifriction additives to improve the tribological properties of lubricating oil. Dong Ling et al. Prepared SiO2 / ZnO composite nano lubricating oil additive by chemical method, and investigated the anti-wear, antifriction and repair properties of this nano additive in mineral oil by four ball machine and ring block tester. The research shows that the SiO2/ZnO composite nano lubricating oil additive has excellent antifriction, anti wear and repair properties. At high temperature, it forms a surface film with low shear strength on the friction surface, thereby reducing the adhesive wear of the friction interface and showing good antifriction, wear resistance and repair properties. Huo Yuqiu et al. Studied the tribological properties of nano silica as lubricating oil additive and found that it can significantly improve the bearing capacity and anti-wear properties of lubricating oil base oil. Chen Shuang et al. Modified the surface of lead oxide nanoparticles with dialkyl dithiophosphoric acid (DDP) and oleic acid, and studied their tribological behavior as lubricating oil additives. It was found that they have good anti-wear effect at very low addition. Sun ang et al. Modified the surface of titanium dioxide nanoparticles with stearic acid. It was found that the nanoparticles modified by organic groups have excellent anti-wear and antifriction ability. Chen Yuezhu et al. Modified the surface of TiO2 nanoparticles with stearic acid and adipic acid, which can significantly improve the antifriction, antiwear performance and bearing capacity of base oil. Guo Yanbao et al. Studied the wear phenomenon by adding nano copper powder into lubricating oil base oil. It was found that there was a dynamic deposition self repair mechanism on the friction surface when nano copper powder was used as lubricating oil additive. Yu Helong et al. Investigated the friction and wear properties of organic modified nano copper particle lubricating oil additives. The results show that the lubricating oil has good anti-wear and anti-wear properties at a certain amount, and improves the bearing capacity of the oil to a certain extent. Fu Xisheng and others prepared oil-soluble nano copper lubricating additives. The research shows that the friction coefficient and wear volume of the lubricating system added with oil-soluble nano copper are smaller than those of the reference oil, and have excellent antifriction and wear resistance. Under the same composite system, the reduction of viscosity can effectively reduce the friction loss power. The simpler way is to increase the viscosity index of the oil, that is, to ensure that the high-temperature viscosity of the oil provides sufficient oil film thickness, reduce the low-temperature viscosity of the oil and reduce the friction resistance in the starting stage of the engine. The energy saving of high viscosity index oil can improve the fuel economy by 0.4% on the basis of the same viscosity friction improvers are divided into organic and inorganic, which are represented by glycerate and modtc respectively. Both of them can effectively reduce the friction coefficient of oil products. Modtc is a multifunctional additive, which not only provides good antifriction, but also has good effects in anti-wear and anti-oxidation. The maximum failure mileage is about 10000 km. There are many kinds of organic antifriction agents, such as glycerate, amide and oleic acid. On the premise of not affecting the functions of other additives, selective use can achieve energy-saving effect otherwise, the strong polarity of antifriction agent will affect the adsorption of functional groups of other additives on the friction pair, and other properties of engine oil are difficult to play. In recent years, with the continuous development of engine material technology, the easily worn parts, such as piston and cam, are sprayed or treated with materials, such as spraying a layer of diamond like carbon (DLC) on the piston skirt, which can effectively protect the harsh wear of the piston skirt. However, because the texture is different from metal materials, it will affect the adsorption of additives, so it is necessary to re evaluate the energy-saving performance of antifriction agents

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