To meet the harsh working conditions of generators, engine oil must have good viscosity-temperature characteristics, adapting to the engine from cold starts in winter to high temperatures of several hundred degrees during full-load operation; good oxidation resistance to ensure lubrication and anti-corrosion capabilities throughout the oil change period, effectively extending the oil change interval; good cleaning and dispersing properties to wash away the gel-like substances and carbon deposits from fuel combustion that adhere to parts, and disperse them in the oil to avoid accumulation; and good wear resistance to prevent wear and scratches on components such as piston rings, cylinder walls, and valve train systems during high-temperature operation. So how do we measure these properties of engine oil? The internationally accepted standards for determining engine lubricating oil are API and SAE. These two standards serve as the identity card for high-grade lubricating oil, indicating its quality and viscosity grades.

API is the abbreviation for the American Petroleum Institute, and the API grade represents the quality level of engine oil. It uses a simple code to describe the working capabilities of engine oil. <BR>API engine oils are divided into two categories: the "S" series represents oils for gasoline engines, which currently include grades SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, and SM; the "C" series represents oils for diesel engines, which currently include grades CA, CB, CC, CD, CE, CF-4, CG-4, CH-4, and CI-4. When both "S" and "C" letters are present, it indicates that the oil is suitable for both gasoline and diesel engines. If "S" is in front, it is mainly used for gasoline engines; conversely, it is mainly used for diesel engines. Whether for diesel or gasoline engines, each increment in letter indicates that the oil's performance is superior to the previous one, with more additives included to protect the engine. API has detailed regulations on the performance characteristics, applicable occasions, testing methods, and standards for each grade of oil. This classification can accurately reflect comprehensive requirements beyond viscosity characteristics, hence it is also called quality classification or performance classification. This classification has strict requirements for testing methods; the higher the oil grade, the newer the applicable engine models, and the higher the emission requirements or harsher working conditions.

SAE is the abbreviation for the Society of Automotive Engineers. Typically, the viscosity grade classification of engine oil according to the "SAE" standard is divided into 11 grades: SAE 0W, SAE 5W, SAE 10W, SAE 15W, SAE 20W, SAE 25W, SAE 20, SAE 30, SAE 40, SAE 50, SAE 60. The number following "SAE" represents the viscosity grade of the oil, with larger values indicating higher viscosity, while viscosity grade and viscosity are not the same thing. Viscosity can be referenced according to the corresponding viscosity grade. If there is a "W" in the number following "SAE", such as 5W/30, 10W/30, 10W/40, 15W/40, 20W/50, 25W/60, it indicates good low-temperature starting performance. This multi-grade oil still has sufficient viscosity at high temperatures to ensure adequate lubrication of all moving parts of the engine.

On some products or materials, you may see the designation SL/GF-3. SL is well-known as the SL grade in the quality levels of gasoline engine oils established by the API (American Petroleum Institute). However, it is unclear whether GF-3 is a typo or has another meaning. Indeed, GF-3 has its special significance. In the early 1990s, ILSAC (International Lubricant Standardization and Approval Committee) was jointly initiated by the American Automobile Manufacturers Association (AAMA) and the Japan Automobile Manufacturers Association (JAMA). In October 1990, ILSAC issued the testing specifications GF-1 for automotive engine oils, and has since established the GF-1, GF-2, GF-3, and GF-4 specifications for gasoline engine oils. GF-1, GF-2, GF-3, and GF-4 not only meet all the requirements of API SH, SJ, SL, and SM, but also must pass the energy conservation requirements set by ILSAC. In simple terms, the GF specification is API specification + energy conservation. This means that SL/CF-3 meets the energy conservation requirements for lubricants. On the other hand, SL/CF-4 is the SL/CF-4 grade of general lubricants for gasoline and diesel established by the API, which is fundamentally different from SL/GF-3 gasoline engine oil.

CF stands for diesel engine oil. Diesel engine oil, like gasoline engine oil, is divided into two-stroke and four-stroke engines. Due to the different structures of the two, the lubricating oils used are also different. To distinguish between two-stroke and four-stroke diesel engine oils, a "2" or "4" is marked after them, meaning CF-4 is suitable for four-stroke diesel engines, while CF-2 is suitable for two-stroke diesel engines. If no number is marked, it does not mean that it can be used for both two-stroke and four-stroke engines; it usually refers to four-stroke oil. However, CF and CF-4 oils were introduced in different years, and the requirements for bench tests are different, leading to different performances. CF-4 oil is suitable for high-speed, modern direct-injection diesel vehicles, generally used in passenger cars and light trucks. CF is suitable for off-road diesel vehicles and non-automotive indirect injection diesel engines.

ILSAC: International Lubricant Standardization and Approval Committee. In the early 1990s, ILSAC was jointly initiated by the American Automobile Manufacturers Association (AAMA) and the Japan Automobile Manufacturers Association (JAMA). ILSAC issued the test specifications GF-1 for passenger car engine oils in October 1990, and has since established the specifications GF-1, GF-2, and GF-3 for gasoline engine oils. GF-1, GF-2, and GF-3 not only meet all the requirements of API SH and SJ respectively but also pass the EC energy-saving requirements set by ILSAC. In simple terms, the GF specification is API specification + energy-saving, meaning GF-4 specification = API SM level + EC energy-saving certification.

In oil product testing, each testing data has a certain range of physical and chemical indicators. However, for specific testing items, there are no specific physical and chemical indicators. For example, in the detection of mechanical impurities in oil product testing, there are no specific data ranges for this test in national standards, industry standards, or enterprise standards. To understand this content, one can only obtain specific data from the tests and indicate "report" in the laboratory report as a reference.

In testing, both the skills of the technicians and the precision of the instruments are indispensable throughout the entire detection process. These factors are also crucial for the accuracy of the overall test results. However, why do two testing institutions produce two different results for the same test under the same conditions? The reason for this situation often lies in the different testing methods used. There are many types of testing methods, but the one prioritized in testing is the one marked with the letter "T". "T" indicates a recommended priority. For example, in the detection of kinematic viscosity, the GB/T265 testing method is used. Therefore, if a non-recommended method is used instead of the prioritized method, the testing results may encounter the aforementioned issues.

"Running without lubricating oil" is a promotional method used by some automotive maintenance product dealers to demonstrate the effectiveness of their anti-wear products through real vehicle tests, allowing car owners to see immediate results. Ultimately, people observe that after running without oil, the vehicle does not experience issues like burning bearings or seizing, while any other potential side effects are left for the dealers to explain. These anti-wear lubricating oil additives are not new; they have been around for several years, with more brands and varieties available than now, and advertising efforts were even greater in the past. Various automotive exhibitions each year feature both domestic and international maintenance product dealers and agents. However, as the number of vehicles in society increases, the market for these maintenance products has not shown a corresponding growth trend; instead, it appears to be somewhat shrinking. What is hindering the development of anti-wear additive products? How scientific are these products? Let's see what automotive experts, manufacturers, and lubricating oil producers have to say.

According to Lin Jian, an expert from Tsinghua University's automotive department, the anti-wear additive products for "running without lubricating oil" were first introduced to China with motorsport. In rally racing, the oil pan of racing engines often leaks due to bottoming out, and to avoid affecting the race, drivers add a "special wear-resistant" oil additive to the engine. When a racing car experiences an oil leak, the special physicochemical properties of the additive can keep the engine running without seizing, allowing the car to reach the service area for repairs and not drop out of the race due to breakdowns. This was originally a temporary measure for special circumstances and does not have universal significance. However, the ability to run a vehicle in a "no oil" state for a short time has been exploited and exaggerated by some commercially savvy dealers as a selling point for promotion in the civilian vehicle sector.

Little do they know, there are many differences between rally cars and civilian vehicles. First, the fuel used is high-octane leaded gasoline, ensuring strong engine power; the lubricating oil is a specially formulated pure synthetic oil of SJ grade or higher, ensuring that the oil's physicochemical properties degrade slowly under extreme conditions such as heavy loads, high speeds, and varying torque, while the use of anti-wear agents is a reactive measure. Secondly, the ignition and electronic control system's computer programs are adjusted to emphasize power, neglecting environmental emission issues, and pursuing excellence in single indicators. In contrast, civilian vehicles focus on a comprehensive balance of emissions, power, and other indicators, emphasizing the durability and consistency of engine use. Special products designed for racing may lead to compromises when applied to civilian vehicles.

Experts from Tsinghua University's automotive department have raised doubts about the anti-wear agents' "no oil driving" claims. They were commissioned by anti-wear agent dealers to conduct performance tests on these products. During the "no oil driving" tests using vehicles like the Jetta or Santana with hydraulic lifter engines, dealers requested to add water to the oil pan, believing that water could serve as a hydraulic working medium. This unscientific request was not approved by the experts. Many dealers often choose vehicles without hydraulic lifters for testing, and they tend to select older vehicles to prevent unforeseen issues. In fact, the dealers themselves are uncertain, and the final judgment on the product's effectiveness is based on whether the engine seizes or not, which has a bit of a "luck" aspect to it and is not a scientifically rigorous test. Will using anti-wear agents for no-oil operation cause excessive thermal load on the engine block? What adverse effects will it have on various engine components? Without disassembling the engine for quantitative testing and analysis, relying solely on driving demonstrations does not clarify any issues and cannot lead to comprehensive, objective, and fair conclusions.

Automobile manufacturers:

According to technical experts from Dongfeng Citroën, the additional components that do not belong to the lubricating oil itself may undergo chemical reactions and produce harmful substances. Will they adversely affect the engine sensors, catalytic converters, and oil filters? Do they have corrosive effects on engine seals? Additive dealers cannot provide convincing product performance analysis reports from relevant authoritative departments. Most rely solely on driving tests for a subjective understanding, making you believe "seeing is believing."

It is said that some dealers tamper with key engine components before demonstrating "no oil driving," and then show you how to "run without oil." In reality, the scene you see of the engine's lubricating oil being drained is somewhat staged; the oil will not be completely drained, and there will still be residual lubricating oil in various parts of the engine, which can provide some lubrication and wear reduction. However, the cooling and cleaning functions will be significantly weakened. At the same time, during actual driving, the speed is required to be controlled within a certain range, and the engine components themselves have a certain tolerance, so serious consequences will not occur in the short term. However, "no oil driving" will definitely cause significant damage to the engine, such as fatigue degradation, premature aging of components, and greatly reduced lifespan. Experts believe that "no oil lubrication" is not a new technology; for example, the sliding bearings made of polytetrafluoroethylene composite materials in automotive shock absorbers; oil-containing bearings made of powder metallurgy in steering columns; and composite bimetal bearings, etc. However, these are mostly used in low-speed areas. In high-temperature, precision, high-speed, and variable load conditions like those in engines, "no oil operation" is still not permitted, and doing so will cause the owner to lose after-sales quality warranty services.

Lubricating oil experts:

According to Zhang Chunhui, deputy chief engineer of Great Wall Lubricants Group, through years of cooperation with automotive manufacturers, a consensus has been reached that automotive manufacturers, especially high-end car manufacturers like Audi A6, clearly state in their user manuals that no unauthorized additives should be added, or the manufacturer will not bear the after-sales service responsibility arising from this. Although most of these anti-wear additive products come from the United States and are labeled with terms like military or aerospace high technology, the three major American automotive companies and companies like Caterpillar and Cummins have repeatedly expressed opposition to the additional addition of such anti-wear additives to engine oil.

Because during the production process of lubricating oil products, various antioxidants, anti-wear agents, anti-foaming agents, etc., have already been added in optimal formula ratios, ensuring the viscosity, anti-wear properties, and other performances of the lubricating oil. They coordinate with each other to achieve a certain balance. If additional components that purely enhance anti-wear properties are added, it will disrupt this balance between components, leading to changes in other properties of the lubricating oil, such as density, flash point, pour point, etc. The negative impact on automotive engines is something that both car owners and manufacturers are most unwilling to see.

Modern cars are highly electronic and intelligent, with various sensors densely distributed. Anti-wear additives containing metal and harmful non-metal components can cause fatal damage to sensors and catalytic converters, and are absolutely prohibited. Some anti-wear product advertisements and descriptions claim to be free of these harmful substances. Other products claim to use nanotechnology, but there are no quantitative experimental reports on the wear reduction principles of nanotechnology in this context. It is unclear whether their addition will affect the lifespan of the engine oil filter, whether the oil change interval will be shortened, or how the degradation of the oil will be affected. Therefore, before anti-wear products undergo extensive and sufficient scientific validation, lubricant manufacturers are hesitant to draw conclusions about them. The simple solution to this complex issue is to not use them. Otherwise, why would we need to develop high-end lubricant products?

It is common for people in the market to take anti-wear testing machines to repair shops or lubricant stores to conduct anti-wear tests to promote internal combustion engine oil. But is this scientific? Can it be said that lubricating oil that passes the anti-wear test is good oil? 1. In the engine, lubricating oil must undergo complex conditions such as high temperature, high pressure, high speed, and high shear, and it must have functions such as lubrication, heat dissipation, cleaning, corrosion prevention, shock absorption, and sealing. Anti-wear performance is just one of many functions; having one good aspect does not mean the product is good. Another important point is that the content of various additives in the lubricating oil must be balanced; one cannot simply increase the dosage of a single additive. The quality of lubricating oil cannot be determined just by seeing how many weights can be added in an anti-wear machine or the size of the wear marks. 2. The National Technical Supervision Bureau does not use this method to test engine oil because this kind of test must consider environmental temperature, motor speed, and also the metal material and surface finish of the sample used. Among these, the main factor is "human" influence; the test materials used may vary, and the equipment may have hidden mechanisms that can adjust the lever arm size to achieve its purpose. 3. The general testing machines for evaluating the anti-wear performance (and friction performance) of lubricating oil have certain limitations when used as anti-wear tests for internal combustion engine oil. Many anti-wear testing machines, such as four-ball machines, Falex testers, and Timken testers, are widely used to evaluate the friction and wear performance of lubricating oil, assessing parameters like friction coefficient, load capacity, and oil film strength. They can be consistent with actual conditions when evaluating gear oil and hydraulic oil. However, using them for evaluating internal combustion engine oil has significant limitations because the wear forms in internal combustion engines mainly include adhesive wear, abrasive wear, fatigue wear, and corrosive wear. The aforementioned wear testing machines primarily assess adhesive wear. Additionally, the forms of friction pairs in the testing machines are ball-ring, ring-block (arc-plane), etc., while in internal combustion engines, they are plane-plane, plane-arc, inner circle-outer circle, etc. The motion forms of the testing machines are mainly uniform rotation, while internal combustion engines have variable reciprocating, rotating, and contact-separation forms. The materials used in testing machines are relatively uniform, while internal combustion engines consist of various cast iron, alloy steel, and non-ferrous metals. Therefore, using general testing machines to evaluate the anti-wear performance (and friction performance) of lubricating oil as anti-wear tests for internal combustion engine oil has certain limitations. In summary, using anti-wear testing machines to detect the quality of lubricating oil is unscientific.

The three key tests for evaluating the quality of lubricating oil are crucial. As a comprehensive standard for assessing the quality of lubricating oil, countries around the world have basically reached a consensus, establishing a basic quality standard system composed of four parts: physicochemical indicators, simulation tests, bench tests, and road tests.

Physicochemical indicators are fundamental. The physicochemical indicators that measure the basic performance of lubricating oil include: kinematic viscosity, low-temperature dynamic viscosity, viscosity index, flash point, pour point, sediment, moisture, foaming tendency, carbon residue, neutralization value, sulfate ash content, and various elemental contents, etc. These physicochemical indicators are merely the most basic metrics for measuring lubricating oil. If the physicochemical indicators are not qualified, then the subsequent simulation tests and bench tests cannot be discussed.

Simulation tests are the preferred evaluation method. First, there are simulation tests. During the development and research of oil products, technicians found that the various physicochemical indicators of the oil products could not explain the issues nor reflect whether the mechanical friction performance was good during use. This main test consists of the following parts: the carbon formation test method and thermal tube test method that reflect the cleaning, dispersing, and oxidation resistance of automotive lubricating oil; the multi-metal oxidation test method and thin film oxidation test method that reflect the high-temperature oxidation resistance of automotive lubricating oil; the spot test method that reflects the dispersing sludge capability of automotive lubricating oil; and the high-temperature four-ball wear test method that reflects the wear resistance level of automotive lubricating oil. These simulation tests can only simply reflect the working conditions of the engine and cannot simulate the impact of complex conditions and working environments, especially the combustion products on the oil performance. Additionally, simulation test methods generally adopt comparative intensified or generalized test conditions. However, intensification may lose authenticity because, during the entire operation of the engine, various comprehensive factors combine to affect the oil's oxidation resistance, cleanliness, dispersion, and wear resistance, which cannot be accurately assessed in a single performance evaluation simulation test method. Therefore, the various simulation test methods and their evaluation indicators are basically not reflected in the specifications and standards of engine oils.

Bench tests reflect issues more realistically. To truly reflect the usage conditions of the oil products and also gain recognition from the engine manufacturing departments, bench tests for evaluating lubricating oil performance have been developed. The bench test involves installing a representative engine in a laboratory and conducting evaluation tests under recognized or certified control conditions for a certain period. Based on the performance indicators agreed upon by the engine manufacturers before the tests, the bench test results are evaluated; it is observed whether the tested oil products meet the requirements. If all judgment indicators of the oil products are within the limit range, it can be considered that the oil product has initially obtained recognition and has obtained a certificate of conformity for that type of oil product. In principle, it can be supplied to the market. After the above three major tests, the quality of the lubricating oil can be fully guaranteed, meeting the requirements of various engine manufacturers for engine oils.

Bench tests reflect issues more realistically. To truly reflect the usage conditions of the oil products and also gain recognition from the engine manufacturing departments, bench tests for evaluating lubricating oil performance have been developed. The bench test involves installing a representative engine in a laboratory and conducting evaluation tests under recognized or certified control conditions for a certain period. Based on the performance indicators agreed upon by the engine manufacturers before the tests, the bench test results are evaluated; it is observed whether the tested oil products meet the requirements. If all judgment indicators of the oil products are within the limit range, it can be considered that the oil product has initially obtained recognition and has obtained a certificate of conformity for that type of oil product. In principle, it can be supplied to the market. After the above three major tests, the quality of the lubricating oil can be fully guaranteed, meeting the requirements of various engine manufacturers for engine oils.

In the performance indicators of vehicle gear oil, apparent viscosity is a very important physicochemical index. Apparent viscosity is related to the low-temperature fluidity of automotive gear oil. During measurement, the gear oil is cooled to a specified temperature in a cold bath, and then its apparent viscosity is measured using a Brookfield viscometer. The temperature is expressed at 150 mPa•s. For example, 75W viscosity gear oil is required to be no higher than -40°C; 80W/90 gear oil is no higher than -26°C, and both 85W/90 and 85W/140 viscosity grade gear oils are no higher than -12°C. Gear oil with excellent low-temperature fluidity can better lubricate and reduce wear on vehicles in low-temperature conditions, avoiding wear on gears caused by overly viscous gear oil.