The word "lubrication" is to solve the friction problem of classical mechanics. Today we have relativity and quantum mechanics, but life for thousands of years has not been able to get rid of the shackles of friction. So in fact, the origin of lubricating oil is no different from the wheels that are parked everywhere on the roadside. Human beings have already lit up the talent tree along the way at the beginning of civilization.
From vegetable oils to mineral oils
At least in the 17th century BC, there were records of the use of olive oil to transport boulders in ancient Egypt, and by the 14th century BC, humans could even lubricate the axles of chariot wheels with animal fat, but limited by the need for food , it was not until the Middle Ages that lubricating substances could be stably extracted from animals and plants. The outbreak of modern civilization began with the sub-industrial revolution, and lubricants in the modern sense have also been reborn with the blowout of oil production.
Peter Kalm
In 1747, the 31-year-old adventurer Peter Kalm accepted a mission from the Royal Swedish Academy of Sciences: to travel to North America on an adventure and bring back crops that would help Swedish agriculture. But a map he drew the following year made him remember in another way. The place on the map later became known as the Spring of Oil Springs. In 1859, Edwin L.Drake built a commercial oil well here. The interesting thing is that the oil well was ignited and destroyed by an open fire more than a month later. Drake had to rebuild it. In today's view, it is a history of human civilization. flare.
Edwin L. Drake Drake's oil wells opened the oil era and accelerated the process of human use of mineral oil. However, the products at that time seemed to be superior, but they were controversial: untreated crude oil could not show good lubricating properties, and could not even compete with large compared to most animal fat products.
Spring in Oil Springs, Pennsylvania, USA
At that time, a German teenager who was preparing to enter the University of Karlsruhe became a turning point after 26 years. As the inventor of the gasoline engine car, Karl Benz started the viral expansion of the automobile market. The booming auto industry is just as booming in demand for lubrication. At this stage, the solvent-refined base oil became the best choice. With the active improvement of various manufacturers, mineral oil eventually occupied the world. In fact, during this period, many well-known engine oil manufacturers were born, such as the well-known Shell. , Exxon Mobil, Castrol, such as BP, Motul, Sheng card and so on.
In a sense, Taiwanese cars came from Mercedes-Benz. At that time, the entire industry did not have a sound standard. The designers sometimes had Su Dongpo and sometimes Li Qingzhao, and the styles of different lubricants were very different. In the process of globalization, there is no unified standard among manufacturers, and they have to pay a great price. So from 1911, SAE (Society of Automotive Engineers) set out to solve this problem and released SAE J300. Today, we can use various grades of lubricants to deal with different models, weather, and regions, and it all starts here.
How does SAE grade oil?
At that time, the maximum working temperature that the lubricating oil could withstand was around 100°C, and the viscosity characteristics of the lubricating oil decreased as the temperature increased. If the ambient temperature was too high, the lubricating oil would be too thin, and an effective oil film could not be formed on the parts. Lubrication protection. Therefore, it is of certain reference significance to select 100°C as the reference temperature to test the viscosity of lubricating oil.
How is viscosity measured? Engineers use a viscometer to run lubricants through specific pipes and measure how long it takes. The parameter that quantifies this process is called kinematic viscosity. For ordinary people, this parameter is not easy to understand, and in fact, when the viscosity difference is not large, the difference between lubricating oil may not be so big, so SAE finally classified it.
The relationship between viscosity and temperature
Viscometer
SAE classification
The performance of SAE30 became the most widely accepted level at that time because it covered the needs of most areas. Lubricants with high or lower viscosity are more used to deal with extreme working conditions. For example, when the temperature of racing engines is high, SAE40 and SAE50 lubricating oils must be used.
Before 1930, lubricating oil could only meet the mileage of about 1500km for automobiles. The problem of insufficient durability prompted manufacturers to speed up the research and development process of additives. At this stage, engineers discovered that zinc and phosphorus could be used as the core of anti-wear additives, while calcium and magnesium The key to cleaning agents and acid-resistant agents, etc., additives greatly extended the life of lubricating oils and were commercialized around 1940, but it was not enough.
From vegetable oils to mineral oils
During World War I and World War II, the blowout of the number of aircraft put forward high requirements on the speed and load of the engine. After the war, these requirements were put on the car. The most obvious manifestation is that the performance of the luxury car has been comparable to that of the car before the war. In parallel, this also means that the demand for SAE 50 in the civilian market has begun to increase. Unfortunately, SAE50 has just enough viscosity to handle high-performance engines at high temperatures, and becomes too viscous at low ambient temperatures. At this point, both engineers and consumers have recognized a problem: the existing classification system is insufficient to describe the low temperature performance of existing oil products.
During World War II, the plastics industry was attached to the rapid development of petrochemical industry, and engineers also discovered the potential of polymer materials at this time: viscosity enhancers can slow down the tendency of oil viscosity to decrease when the temperature rises. For example, the SAE30 lubricating oil has been modified to not only ensure its low temperature performance, but also achieve the viscosity of SAE 50 in high temperature environments. In order to distinguish whether the lubricating oil has undergone this treatment, in 1952, SAE began to carry out compound grading of this oil, Winter is coming, and "W" can appear.
SAE 30 lubricating oil is also equivalent to SAE 20W30 because it can meet the environment above -10 ℃. If it is transformed to meet the SAE50 standard, it will become SAE20W50. This grading system was quickly accepted by the industry, and the most popular SAE 30 before the war became SAE 20W50 after the war.
Early oils of this composite grade also had a drawback: the viscosity enhancers were easily oxidized to harmful substances. Faced with this fact, the answer people found was fully synthetic motor oil, but at that time its price was often more than three times that of ordinary motor oil, which was difficult to promote.
How is the SAE compliance level perfected?
With the popularity of compound grade oils, SAE realized the limitations of J300: compound grade oils have very different viscosity properties under high temperature and high pressure conditions than single grade oils, and some compound grade oils tend to fail at high temperatures. So between 1970 and 1975, SAE revised J300 and added a 150°C ultra-high temperature test. As for the continuous progress of lubricating oil technology, the changes in this standard are constantly being promoted. The strictness of the past can make us today have a better basis.
Today, SAE J300 recognizes oil without viscosity enhancer as a single-grade oil, and defines 6 winter grades and 5 summer grades. The test methods and units used for these two types of grades are different, so like 0W40 and A composite-level product such as 5W40 must pass two levels of tests at the same time.
In the summer level test, in order to ensure that the oil has enough energy to cope with the process of increasing temperature and thinning viscosity, higher grades are preferred by consumers. But as mentioned before, the grade is defined by a certain viscosity range. For example, the following four brands of oil, although the grades are the same, are 0W40 or 5W40, but the viscosity of 3M is significantly higher, S Cards and C cards are comparable. It's a bit like an exam, where 95-100 points are considered A+, and 100 points are a bit different from 95 points.
High temperature oil viscosity performance
If the viscosity is too high in a low temperature environment, it will cause the oil to have poor fluidity when the engine is cold started, and the parts cannot be lubricated in time, so the grade with lower viscosity is better. As you can see in the picture, 5W40 has higher viscosity than its own 0W40 products due to the large winter grade label value. When determining the grade, the low temperature fluidity is also different. Among the fully synthetic products of 0W40 and 5W40, 3M is superior to several other products, while the semi-synthetic products of 5W40, the S brand has a slight advantage.
Low temperature oil viscosity performance
Before the 1960s, apart from the SAE viscosity classification, there was no effective standard to control the quality of oil: there was not only one way to extract paraffin from crude oil, and the components of the base oil were also different. For example, some The high solubility of particles is not easy to generate impurities, and some aromatic
What is the API (American Petroleum Organization) classification system?
As far as gasoline engines are concerned, API defined the oil before 1960 as "SB", but at that time there was still a high grade called "API Service MS", which was modified after 1968 to what we call today. API SC", or "SD".
This standard has been revised and abolished in many versions since its appearance. Today, only SJ in 1996, SL in 2000, SM in 2004 and SN in 2010, the most demanding, are left.
Base oils are divided into several categories according to different production processes: solvent-refined base oils actually contain two sub-categories with high and low aromatic hydrocarbons, and the viscosity coefficients of these base oils are very low. , and the sulfur content is high, which is not environmentally friendly; the second-class base oil is hydrotreated, which is purer and more stable than the first-class base oil, and contains almost no sulfur; the essence of the third-class base oil of hydroisomerization is still Mineral oil, a relatively good product, is also comparable to synthetic motor oil, but it also has many shortcomings.