About Motor Oil

About Motor Oil

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Due to the fact that the engine plays the most important role in vehicle movement, it is important to pay attention to its health. As you know, the engine plays a vital role in combustion of the vehicle from power to gear. All engine power comes from engagement and the connection of parts to each other. For such parts, the presence of friction means the loss of energy, corrosion, and shortening the life of the components. Therefore, experts have always sought to find a way to reduce this friction. Because of the properties that it has, it has a significant impact on friction reduction and is one of the most effective achievements of experts in this field. But the production and production of oil that can work in high-pressure and high-pressure engine conditions requires technical knowledge. On the other hand, this oil should not lose its quality under the influence of environmental conditions, and should be faced with a loss of efficiency. Considering these, we find that the engine oil is produced in a complicated process.

Originally engine oil was only used to lubricate engine portions, but with the observation of damages such as rust, corrosion and sedimentation of engine parts, experts were thinking of producing lubricants with more capabilities, which we will continue to describe.


Viscosity, known as viscosity or viscosity, is one of the most important characteristics of engine oils. Viscosity can be determined by the resistance of the fluid to the motion. The viscosity of the fluids is correlated with the temperature, and the higher the temperature, the lower the viscosity, and the fluid becomes looser. This is the main reason to be taken seriously when choosing an engine oil. Engine starts to start when the engine starts, and the oil must start the lubrication quickly; otherwise, it will cause serious damage to the engine. However, if the oil increases the viscosity due to the low ambient temperature, it cannot move quickly and cause the moving parts to lubricate; on the other hand, the high temperature of the environment also reduces the viscosity and causes the oil performance to be difficult and the oil cannot cover the parts well. To prevent such problems that occur when the vehicle is turned on, insert the viscosity of the oil on the package.

What are the main standards in choosing the right engine oil?

Engine oil quality index based on API

The word API (API) is the American Petroleum Institute, which means the American Petroleum Institute. This name has become a standard for determining the quality level of engine oils. For the gasoline and diesel engines, the API has a unique symbol. For gasoline engines, the letter S is used, and for diesel engines, the letter C is used; therefore, if motor oil is suitable for a gasoline engine, it starts with API S and suitable oils for diesel engines begin with the term "API C". But that's not all, and the quality of the oil cannot be recognized. In this standard for gasoline engine oils, after the letter "S" comes, letters A through N, and for diesel engines, after the letter "C", a letter A to J is inserted. In this classification, as it goes toward the letter A, the quality of the oil is reduced, on the other hand, moving towards the letters N and J indicates a rise in the quality level; hence, an API-SN grade oil of petrol engine has the highest quality, but API SA, shows the lowest quality. This classification for diesel engines also begins with the API CA, which has the lowest qualitative level, and ends with the API CJ, which has the highest level of quality. It goes without saying that for two-stroke and four-stroke diesel engines, numbers 2 & 4 are used in front of the last letters, for example, an oil with API CJ-4 API are designed for four-stroke diesel engines, and because of its very high quality, the letter J has been inserted.

Note: It is best to use motor oils with a higher quality index for your motor vehicle. At present, the highest quality engine oil produced is indicated by SN. In the not-too-distant future, this index may be enhanced to SO by the advancement of engine oil technology.


API standard progress schematic

نمودار پیشرفت شاخص API

SAE standard in viscosity of engine oils:

The Governor (SAE) stands for the Society of Automotive Engineers, which means the Association of Automobile Engineers. This standard is composed of numbers between 0 and 60, and in some cases the letter W is also displayed. The SAE standard is a determinant of viscosity of the engine oil. The number 0 in this standard shows the lowest viscosity and indicates an easily flowing oil, instead of 60, the viscosity is increased, and the SAE 60 is a very oily viscosity indicator, which means it is hardened. The use of the letter W in this standard is also used to indicate the minimum winter viscosity that comes with the word "winter". Now, with the knowledge of these standards, we can explain two different viscosity types that are included on the motor oil. Engine oils can be divided into monogrid and multigrid groups according to the type of viscosity.


غلظت روغن موتور

Concentration of engine oil.

 Monogrid motor oil

Due to its structure, this oil cannot change its viscosity within a temperature range and is only used for a specific temperature or seasonal term. Monogrid oils are old, and in the past, they were the only engine oil produced for motor vehicles. Generally, SAE grades from 0 to 30 were used in cold seasons and low temperatures. If a person uses this oil in his car, he had to change the engine oil by warming up and replace it with an oil with a particle size of over 30 SAE. Although these oils did not have a high price, they lost their effectiveness when they changed, and they were not a reliable option in all seasons.

Multigrid motor oil

By observing the weak points of the monogrid oils, experts began to develop a more flexible product against temperature. This was accomplished by changing the structure of the engine oil, and new oils that did not lose their performance during the four seasons. These oils, which are considered by the public and the manufacturers, are distinguished from two viscous particles that are separated by the letter W. The first number represents the level of viscosity in the warm season and the high temperature, and the second number represents the viscosity in the cold season and the low temperature that we mentioned in the SAE standard. The owners of the car, however, did not worry about temperature changes at all, because the structure at low temperatures prevented hardening and increased viscosity of the oil and did not result in a sharp drop in viscosity at high temperatures. To clarify this, we will examine the engine oil of 10W-40.

The number 10 represents the minimum viscosity of this product in the warm season and the high temperature, and the number 40 shows its maximum viscosity in cold and low temperatures. This product can also be compared with another 20W-50 motor oil. As it is known, the second engine oil has a higher viscosity due to the number 20 in the heat season and is stiffer than the 10W-40 oil. Therefore, the 20W-50 oil is suitable for warmer environments because the oil is not too loose, this can be achieved by comparing W 50 with W 40. The 10W-40 oil in the cold season will have a viscosity of 40, while the latter for the second oil is 50, indicating that the 20W-50 oil in the cold is tightened more than its counterpart, so this oil is more suitable for places that do not have very cold winters. It is better to use 10W-40 motor oil in extremely cold environments.

Note: Oils of low viscosity engines are considered as light oils. These oils reduce the fuel consumption and engine smoothness. Of course, the type of engine and its production technology are of particular importance. For example, in most Japanese, Korean and European cars, light engine oil (5W-20.5W-30) is used for engine running due to high engine production.

SAE & API standards schematic

The oil base factor:

The process of producing each engine oil is different from the other engine oil. Oil The engines produced according to the type of motor oil base are divided into 3 types.

• Mineral Motor Oil

Semi Synthetic Oil

• Synthetic motor oil (Full Synthetic)


 Mineral Motor Oil

Perhaps it can be said that this type of engine oil is the first engine oil produced in the process of its production has not been optimized. In fact, this engine oil is produced on the basis of crude oil and without the reform of the chemical structure to enter the market. This is an engine oil for old and classic cars. Due to the low cost of the engine oil, but because of its simplicity, the time interval between two engine oil changes is shorter.

Semi Synthetic Oil

This engine oil is a combination of synthetic motors and simple motor oils (minerals). The synthetic chemical structure of synthetic engines has been substantially modified to increase its resistance, durability and efficiency. The use of this engine oil is used in today's cars, but not least expensive. This type of motor oil is for cars like Peugeot 206, Peugeot 405, Peugeot Pars, Samand, Tiba, Mvv and more. It is suitable. The price of this type of motor oil is higher than that of the miner engine, and its replacement interval is longer.

Synthetic or synthetic motor oil (Full Synthetic)

This engine oil is based on the latest technology in the production of engine oil, with all impurities of the engine oil completely removed and its chemical structure has been strengthened, which has a higher resistance to lubrication than the rest of the engine oil. The general benefits of Synthetic Oils are long lifespan, high resistance to oxidation, helping to reduce fuel consumption, avoiding corrosion, non-toxicity and good performance. All synthetic motors are specially designed for high-tech cars, such as Benz, BMW, Toyota, Honda, Hyundai and Kia, and so on, this engine oil should be used.

The price of this motor oil is much higher than that of mineral oils and semi-synthetic motors.

Although all-synthetic engine oil is more efficient in terms of performance, the choice of this engine oil is not suitable for some cars, or it is not necessary to buy this type of engine oil, as only additional costs will remain on your hands.

Synthetic oil was first produced massively by the Germans during the Second World War. Due to the lack of oil, the German government produced coal oil and methane gas, which, due to the good adhesion of oil molecules, used it for aircraft engines. Later, with the advancement of technology and improved filtration process, synthetic oil became synthetic oil.


Different engine oils produced based on the type of motor oil base:

 The chart below demonstrates the multigrid oil viscosity’s relation with different temperatures:

Summer Monogrid Oils

Max. temperature in centigrade

Min. temperature in centigrade




SAE 20



SAE 30



SAE 40


Winter Monogrid Oils

Max. temperature in centigrade

Min. temperature in centigrade















All season Multigrid Oils

Max. temperature in centigrade

Min. temperature in centigrade


Max. temperature in centigrade

Min. temperature in centigrade


Max. temperature in centigrade

Min. temperature in centigrade




SAE 0W-30



SAE 5W-20



SAE 5W-30



SAE 10W-30



SAE 10W-40



SAE 15W-40



SAE 15W-50



SAE 20W-50


 May we add mineral oil to synthetic motor oil and would it be working properly?

Suppose you're on a trip and suddenly the engine oil check light turns on. After review, you will notice that the engine oil volume is less than usual and you will have to add it to the engine oil, but you may not be able to find the same oil in the engine oil tank. For example, you have used synthetic motor oil, but the only thing you have is a mineral oil. According to a recent study by Mobil One, one of the forerunners in the production of motor oil, adding these oils will not be problematic. In fact, these oils are compatible in some way and do not come into contact with gel mixing. In fact, most of the engine oil produced is a combination of natural and synthetic oils, and adding them together will not hurt your engine. But it's better to change the time of the engine oil change and do it sooner. Because they interact with each other due to the various additives in the engine oil and do not work well when combined.

If you have to add engine oil, it is recommended to add the same brand and grade to the engine oil tank. Because different brands use their own special supplements and may not be compatible with other motor oils. If your engine oil grade is 10W-40, it is advisable to use the same grade. Otherwise, if you had to, you could use the same brand and grade as the engine oil inside the tank.  It’s also possible that the production year is mentioned after the “ACEA” grading as 04 or 07. Many sport car oil engine cans proudly display the many certificates, achieved by vehicle manufacturing companies.

ACEA standard system

This standard system is designed for European cars and replaces the former CCMC system. ACEA delivers engine oil into three categories. One for the gasoline engine (letter A) and the other for diesel engines (letter B) and the next for heavy duty diesel engines (letter E).

ACEA's motor oil and its characteristic

A1: Economic Fuel Consumption Level

A2: Standard Performance Level

A3: Superior performance or long oil change intervals.

A5: combining both the A1 and A1 grades (economic fuel consumption and the long oil change interval potentials)

B1: Fuel Economy

B2: Standard Performance Level (Outdated)

B3: Excellent performance or high fluidity and durability

B5: A combination of B1 standards plus B3 / Long oil change interval capability

Not suitable for all engines - should only be used in engines that mention this degree of fuel efficiency.

Mineral oils: 

E1   Diesel Car Bosch without turbocharging

E2   Standard performance level

E3   High performance / Long-term oil change intervals

E5 (1999) High performance / long-term oil change intervals plus API America performance. This is the first global attempt of ACEA.

E7   Euro engines 4 - After-operation drainage (EGR / SCR)

Synthetic / synthetic partial oils (industrial part)

E4   Higher performance and longer oil change intervals

E6   Euro specs 4 – low SAPS for vehicles with DPF

 Diesel with Low SAPS (Sulfate Ash, Phosphor, Sulfur): 

In diesel engines, with a diesel particulate filter (DPF) - an exhaust filter unit that takes microscopic soot particles). Normal diesel oils, used in DPF engines, can cause the filter to be blocked by ash.

C1: low SAPS value (0.5% ash) Fuel efficiency;

C2: Medium SAPS (0.8% ash) Cost-effective fuel consumption & performance;

C3: Medium SAPS (0.8% ash).

Do you need to add auxiliary engine oil?

Most motor oil companies have been able to boost their performance by overtaking their rivals by adding special supplements to their engine oils. So, if you use high quality engine oil, you do not need to add auxiliary engine oil. Of course, some supplements are specially developed to eliminate defects. For example, a nano-prototype motor oil supplement has been developed to protect and prevent engine oil leaks. If the engine is leaking, the use of engine oil supplements can solve the problem to a great extent.

Authentic motor oil brands

Among the well-known companies that produce engine oil, Edinol, Totals, Castrol, A, Shell and Lycomolelles are mentioned. Also, among the Iranian brands in the field of motor oil production, Behran has been able to compete with foreign products in the Iranian market by producing quality oil. 

Tips on engine oil

Never use a combination of several engine oils.

After turning on the vehicle, do not move immediately and take 20 seconds to lubricate the oil (that is, warm the car).

It is advisable not to use additives for motor oils unless it is fully compatible with engine oil.

Never use oil that spans more than three years from its production date.

If the engine oil is not black, it's not a sign of its quality, but its lack of ability to absorb particulates and contaminants and it is better to change.

The type of engine oil (mineral, synthetic, semi-synthetic) must be selected according to the vehicle's manual or engine compartment label.

In selecting engine oil, the climate conditions should be considered.



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