One of the main indicators characterizing engine oil is viscosity. Motorists are familiar with the situation in which the engine cannot be started in cold weather. The starter rotates the crankshaft very sluggishly and the lubricant gets stuck in the channels of the power unit. This means that the lubricant has a high viscosity, which is not suitable for operation in the winter season.

In this article, we will consider the main characteristics of motor oils using such popular oils as 5w40 and 5w30 as an example, and at the end we will separately consider how 5w40 oil differs from 5w30 and which one is better to choose.

By seasonality, motor oils are classified as follows:

• summer oil. It has a high viscosity index, therefore it is effective at positive temperatures, but if the thermometer falls below 0 degrees Celsius, it will be difficult to start the engine.
• winter oil. Due to its low viscosity, the lubricant makes it easy to start the power unit even in severe frosts, but it is not effective in summer because it creates an oily film that is unstable at positive temperatures.
• All-weather oil. A universal energy-saving lubricant that does not need to be changed depending on the season, because in summer it acquires a high viscosity, and in winter - low, reliably protecting the engine all year round.

Viscosity is the main indicator on which the quality characteristics of the oil and its cost depend. You should choose the lubricant that harmoniously combines optimal viscosity indicators and additional components that increase the life of the power unit.

Car manufacturers give recommendations on the use of certain types and brands of automotive oils. To find out which lubricant to use in summer or in winter, just read the car's operating instructions. But this rule has an exception. Technology does not stand still, which means that the brands of oils also change, so the data indicated in the instructions for a used car may become outdated. In this case, the lubricant must be selected independently.

SAE oil classification

In lubricant catalogs and in the recommendations of car manufacturers, the abbreviation SAE often appears. This is not a manufacturer's brand, but a specification developed by the Society of Automotive Engineers (SAE - Society of Automobile Engineers).

The classification does not prescribe on which vehicles a particular type of lubricant should be used, it only sorts oils according to the degree of viscosity, which depends on temperature:

• summer oils: 20, 30, 40, 50, 60;
• winter oils: 0W, 5W, 10W, 15W, 20W, 25W;
• All season: the name consists of two parts, for example, 5W40.

The letter "W" in the classification indicates the use of lubricants in the winter (Winter). So what does the 5W30 designation indicate? The fact that 5W is a viscosity characteristic in winter, and 30 is a temperature indicator that is optimal for the summer season. It depends on the first part of the specification how easy and painless it is for the power unit to start it up in the cold season. The second part indicates at what highest temperatures the film between the engine parts will maintain a stable structure.

Which oil to choose 5w30 or 5w40

The choice of lubricant made according to the SAE specification largely depends on the temperature of the area where the vehicle is operated. The winter coefficient, for example 5W, determines the lowest temperature at which the engine will operate without failure. For 5W, this is -30 degrees Celsius, depending on the "summer" characteristics. Proper selection of lubricant keeps the power unit from jamming and premature failure. Hardened grease makes it difficult to rotate the crankshaft with a starter. The oil pump is not able to drive the frozen mass through the lubrication channels. The fluidity of the lubricant must be sufficient so that it does not turn into a "jelly". 0W oil has an ideal viscosity indicator for the winter period.

There are subtleties in choosing a summer indicator. Too fluid lubricant will not linger on the mating engine components, which can lead to overheating and premature engine failure. The summer coefficient, for example, 30, indicates the minimum and maximum viscosity of engine oil at operating temperatures of 100-150 degrees Celsius. The higher this number, the higher the viscosity of the oil at high temperatures. More on this below.

Video about the differences between 5w30 and 5w40

The difference between 5W40 oil and 5W30

If we talk about the differences between 5W40 engine oil and 5W30, then first of all it should be noted that they have the same characteristics responsible for starting the engine in the winter. Both oils are classified as 5W, which means that such oil can be used at temperatures down to -30 degrees Celsius. As for the second part of the marking, then you should refer to the SAE oil viscosity table.

As can be seen from this table, the kinematic viscosity of 5w30 at 100 degrees Celsius is in the range of 9.3 - 12.5 mm sq. / s, while 5w40 has a viscosity of 12.5 - 16.3 mm sq. / s. The minimum HTHS viscosity for 5w30 is 2.9, while for 5w40 this parameter can be 2.9 or 3.7.

It is not difficult to notice that at high temperatures, 5W40 oil differs from 5W30 in viscosity. 5W40 oil is more viscous, which means it forms a thicker film on the cylinder walls. On the one hand, this is good, but if the oil is too viscous, there may be problems with its flow. Therefore, in the matter of choosing an oil between 5W40 and 5W30, it is better to trust information from the car manufacturer.

Inexperienced drivers and vehicle owners are often interested in the question: how exactly are the markings of different types of oil deciphered.

As a rule, all oils for automobile engines are marked, which consists of two numbers and the letter W between them, it looks approximately like this: XXWYY, where XX and YY are the indicated numbers.

In this case, we will analyze the SAE 5W30 class oil. Looking ahead, it is worth noting that SAE is the name of this classification, which inherited its name from its developers.

SAE World Classification

According to the SAE classification accepted all over the world, automobile oils that are intended for all-weather use are marked in the way described above.

By and large, the first number indicates the viscosity of the oil at low temperature operating conditions, and the second - the viscosity in working condition at high ambient temperatures.

Recognized as the main one in most countries of the world and accepted as international, this classification system was developed in the United States of America. The development of this classification was undertaken by the Society of Automotive Engineers of the USA - Society of Automotive Engineers, abbreviated as SAE. It is SAE 5W30 (on an example) - the most traditional designation of the oil class, although there are others.

In addition to the SAE classification, a number of classifications have been adopted, which are based on the type of fuel for engines and the year the car was developed. But these are other directions of classification. In this case, the decoding of oil marked 5W30 can only be done according to the SAE standard.

The letter W just means the word Winter (winter), which just indicates that the motor lubricant belongs to the viscosity class, which is intended for use in low-temperature conditions.

Using the example of SAE 5W30 oil, you need to understand that the number 5 corresponds to some of the parameters that this oil has. Of course, the number 5 is not some single parameter of viscosity or temperature, this parameter is combined (composite), since it characterizes several criteria at once that are necessary for classifying engine oil.

What do both options mean?

Firstly, this oil classification parameter indicates the rate of lubricant pumping from the moment after the start. It also shows how quickly the oil enters the working units of the engine. At the same time, this parameter also indicates the amount of necessary battery energy that is used to drive the starter into working condition (in this case, to a temperature of 40 degrees Celsius).

The second number, which is usually indicated after W (sometimes the parameters are separated by a dash, which is correct, and sometimes not), corresponds to the summer or as it is also called the high temperature engine operation. This oil viscosity grade shows its main characteristics at engine operating temperature - in the heating range of about 100 degrees Celsius.

Unfortunately, it is impossible to simply measure these parameters, since these values ​​are only classes that can also correspond to a whole set of oil characteristics.

In order to indicate these numbers, the oil is measured in a complex, including determining, for example, dynamic viscosity and kinematic, as well as other indicators. It should also be understood that the class corresponds not to one value of operating temperatures, but to some of their range. Therefore, even oils with the same viscosity grade may differ in some of their characteristics for different engines, or with differences in temperature, they may show different results.

Decoding SAE 5W30

The accepted classification assumes that SAE 5W30 has a number of characteristics. It is worth disassembling them separately, and first of all, the designation 5W (from the range from 0W to 20W) foresees the correspondence of a certain temperature range (in total, temperatures from -35 to -10 degrees Celsius are foreseen).

• 5W is one of the lowest temperature viscosity grades, which allows the engine to be used in fairly severe frosts. The temperature for this class of oil at -30, -25 degrees Celsius is quite comfortable for work.
• High temperature viscosity (in this case 30) indicates the suitability of the oil at temperatures of 2025 degrees Celsius.

Thus, 5W30 oil is well suited for conditions in northern countries with fairly low temperatures, but without extreme heat in summer.

The selection of engine oil is an important task for any motorist. The simplest tip for oil selection is to follow the advice of the car manufacturer. But when it is not possible to fulfill this recommendation, then you have to deal with the properties of the oil and its markings.

In this article, we will look at 5w30 and 5w40 engine oil and try to figure out what is the difference between these two brands.

The first number from the marking of engine oil characterizes its viscosity when used in the cold season, and the second part characterizes the fluidity of the oil in the warm season, at high temperatures. This marking characterizes engine oil according to the widely used SAE (American Association of Auto Engineers) classification. Two numbers in the marking mean that both types of oils are all-weather. This versatility is the reason why 5w30 and 5w40 oils are so popular with motorists.

Engine oil marking according to SAE classification

Viscosity at low temperatures. This most important property is described by the first part of the 5W index, where W is winter. At low temperatures, engine oil, like most fluids, thickens. The stronger the viscosity, the more difficult the operation of the oil pump. For the types of oil we compare, the first index is the same. When turning, the maximum viscosity of such a lubricant at -35 ° C is 6600 MPa, and when pumping, the indicator reaches 60,000 MPa.

high temperature viscosity. This is the second part of the oil label. According to the SAE classification, for 5w30 at 100 ° C, the oil viscosity (kinematic) will be in the range of 9.3 - 12.6 mm sq. / s. For grease type 5w40 12.6 - 16.3 mm sq./sec. High-temperature viscosity is characterized by another indicator: the minimum viscosity at a certain shear rate (10 6 s -1). For 5w40 oil, this figure (3.50) is also higher than for 5w30 (2.9).

What is the difference between 5w30 and 5w40

As already mentioned, 5w40 oil is more viscous and less fluid at high temperatures. That is, when the piston passes, the film remains thicker on the cylinder walls than when using 5w30. This is a basic difference between 5w30 and 5w40 as they behave the same at low temperatures. However, a thicker film is not always a plus.

Marking engine oil 5w30 and 5w40 on the canister

What happens if you use oil with a higher or lower high temperature viscosity in the engine than indicated in the user manual:

• With a higher viscosity, the resulting film on the internal surfaces will be larger than required. In some places, the lubricant simply may not flow due to too much viscosity. This, of course, is bad: it can threaten premature wear of parts, an even greater increase in the operating temperature of the engine. Such troubles threaten if you fill in the 5w40 brand where 5w30 is recommended.
• In the opposite case (using 5w40 instead of 5w30), less lubricant is consumed for waste. In principle, this lengthens the service interval, as indicated by some manufacturers and sellers of motor oils. But, if the car manufacturer recommended 5w40, then the 5w30 brand may form a too thin film on work surfaces. As a result, too rapid wear of the engine cylinder walls and piston rings can occur.

Video about the difference between 5w30 and 5w40

What is better 5w30 or 5w40

The purpose of using engine oil is to form an oil film on all rubbing engine parts. Very small gaps (a few microns) in the engine between rubbing parts require constant high-quality lubrication, excluding dry friction. What brand of lubricant is best for your car, only the manufacturer knows. When recommending a certain type, manufacturing companies take into account not only the characteristics of the oil, but also the design features of the engine itself. Therefore, it is best to follow the manufacturer's recommendations.

It should also be borne in mind that in addition to the SAE classification, lubricants must also meet the requirements of other systems: ACEA, API. Labeling for these classification systems is always indicated on the packaging, but attracts less attention.

As for specifically 5w30 or 5w40, we can say the following. 5w40 oil keeps the film perfectly and eliminates dry friction. It is well suited for modern motors with high thermal stress. 5w30 oil has a lower viscosity. It makes it easier to start the engine in cold weather, but becomes too fluid in hot weather. At a temperature of about 120 - 140 degrees in the engine, the viscosity of 5w40 auto-lube is 1.5 times higher than that of 5w30.

The car engine needs constant lubrication and protection of components from frictional forces. For the normal operation of the power plant, lubricants are needed to protect the motor parts from excessive contact. If the technical fluid is selected correctly, then the service life of the unit is noticeably increased. In the market of branded lubricants, motor oil 5w30 occupies a leading position in terms of demand among products of synthetic origin.

Any lubricating motor fluid has its own classification and specifications, this must be considered before purchasing a product. Allocate lubricants designed for gasoline engines, diesel engines. In addition, there are universal compositions that are combined with any type of power system, including diesel installations. Motor lubricants by their nature are divided into mineral composition, semi-synthetic oil and synthetics.

Today, drivers, when choosing a consumable, do not know how the marking of the motor mixture is deciphered. Let us consider in detail what kind of decoding SAE 5w30 has, what each of the numbers means, what is the meaning of these values.

Temperature range of use of engine oils

There are special requirements for motor lubricants. Among the main physical parameters, the viscosity of a substance and its temperature regime are distinguished. In developed countries, the SAE classification is used, which takes into account the viscosity-temperature characteristics. 5w30 synthetic oil is marked according to the SAE system. The designation for this classification establishes the operating temperature range of the material.

According to SAE, all motor lubricating fluids are divided according to the seasonality of operation:

• Winter blends. The low viscosity of the oil ensures guaranteed engine start at low temperatures.
• Summer compositions. Due to its high viscosity, the solution reliably lubricates the vehicle's propulsion system at high temperatures.
• Universal (all-weather) materials. Automobile oils are used both in winter and in summer.

What do the numbers mean? According to this classification, all motor mixtures are divided into 12 groups, including 6 winter categories (0w, 5w, 10w, 15w, 20w, 25w) and 6 summer viscosity groups (10, 20, 30, 40, 50, 60). For multigrade automotive oils, two numbers are indicated in the designation. The first characterizes the properties of the composition in an environment of low temperatures, and the second shows the viscosity of the component in the summer. 5w30 oil decoding:

• The first digit 5 ​​in the product labeling indicates the minimum temperature regime at which the parameters of the substance do not change. In our case, the lower temperature limit is not lower than 30 degrees below zero.
• The letter designation "W" indicates that it is desirable to use the lubricant during the cold season. It turns out that SAE 5w engine oil belongs to the winter category of lubricating components.
• The last digit corresponds to the temperature limit at which the lubricant functions normally. SAE 5w 30 engine oil indicates that it is only applied up to 30 degrees Celsius.

5w30 oil decoding makes it clear that the mixture can be used at temperatures from -30 to +30 degrees Celsius. To obtain a substance with desired viscosity-temperature properties, a special package of additives is required. Additives are able to thin the technical solution at low temperatures and thicken at higher values.

Specifications

Engine oil in the engine

Motor oil 5w30 has a lot of advantages. The excellent performance of this component helps to cope with the adverse operating environment. Adverse effects on engine parts are considered:

• prolonged operation of the vehicle at idle;
• constant stops and traffic jams;
• increased gas pollution and dustiness of the area.

Thanks to the synthesis reaction of a set of additives and a universal structure, motor oil 5w30:

• protects the mechanisms and elements of the engine from mechanical and chemical effects;
• forms a stable oil film on parts;
• slows down oxidative and corrosion processes;
• relieves working surfaces of soot and other deposits;
• cools the system nodes properly.

Engine oil 5w30 impresses with its characteristics. When choosing a lubricant for a car power unit, you need to pay special attention to its technical documentation. These acts contain the manufacturer's recommendations for the operation of the engine. The same document establishes tolerances for automotive oils, but you need to remember that the manufacturer's recommendations are aimed only at the "heart" of the car.

Chemical base

7TOTAL Quartz INEO 5W30

The complex of additives included in the composition of SAE 30 lubricants perform strictly specified functions in specific types of propulsion systems. The additives used comply with all regulations and regulatory standards. Choosing a consumable for your car is an individual decision for the driver. He takes into account some of its technical characteristics and chooses a lubricant according to his taste and natural origin. It is widely believed that 5w30 mineral oil in used cars leads to reduced consumption of consumables and increased engine life. Synthetics or semi-synthetics are used for more modern cars, but it all depends on the owner. If the owner’s power plant has not yet been run-in, then it is recommended to use synthetic compounds. SAE 5w30 synthetic motor lubricant is also in this category.

It is worth noting that before obtaining a quality certificate, a test of 5w30 oils and their chemical analysis are performed. As a result of tests of SAE 5w30 engine oils, it is possible to accurately simulate real operating conditions and record the results. The product packaging contains all the necessary information on the compliance of the properties of the lubricant mixture with the stated requirements. Tests of synthetic motor oils reveal to buyers the technical parameters of purchased mixtures from different manufacturers. No one is safe from buying a low-quality product, which means it is easy to fall for the bait of an unscrupulous seller, so you should not buy motor oils at unverified points. It is more rational to visit official points of sale, where the possibility of purchasing fake engine oil is reduced to zero. Before buying a product, you should carefully examine the packaging for scuffs and scratches, deformations of the lid and the information label. Let's consider the description of some popular auto blends, where the optimal ratio is in terms of the quality of motor oils and the price:

• ZIC XQ 5w-30. Lubrication is all-weather and is intended for a turbocharged engine (turbocharged installations) or without it. The oil combines two main functions - this is the reliability of the engine and economical fuel consumption.
• General Motors Dexos2 Longlife 5W30. A feature of this substance is the high lubricity of parts of the power unit, which allows you to operate the car in difficult conditions.
• TOTAL Quartz INEO 5W30. The mixture is distinguished by sulfate low ash content. Thanks to this characteristic, fuel is saved and emissions of harmful substances are reduced. The component is intended for both gasoline and diesel systems.

Summing up

Synthetics SAE 5w 30 is a demi-season lubricant mixture. Due to this property, motor oil 5w30 is applicable year-round, even in conditions of unexpected temperature changes in the off-season, while maintaining all its “useful” functional characteristics in any type of engine.

Among car owners, 5w30 and 5w40 engine oils are considered the most popular brands, but not many people know what the difference is between them and what the oil label means. This is an important question, so it’s worth figuring out which oil is better.

What does the marking of engine oil 5w30 and 5w40 mean?

So, the first digit from the oil marking indicates its viscosity at low temperatures, the second part indicates the fluidity of the substance in the warm season. This engine oil marking characterizes it according to the common SAE classification.

The numbers in the marking indicate the type of oil - both types are all-weather, this is the reason for its high popularity among motorists. This class of lubricating fluids is universal (all-season); it can be used in engines with any type of fuel at any temperature.

Decoding oil 5w30 and 5w40

Viscosity at low temperatures. The viscosity parameter is very important for the machine, since it determines the ability of the lubricant to remain on the surface of the motor for a long time. The most important property of engine oil is described by part 5 of the 5W index, and W means winter (winter). In cold weather, engine oil thickens. The stronger its viscosity, the more force the oil pump works. In these types of oil, the marking has the same first index.

high temperature viscosity. This parameter characterizes the second part of the marking. According to the established SAE classification for grade 5w30 at t 100 ° C, the viscosity of the substance will be from 9.3 to 12.6 mm kV / s. For brand type 5w40 from 12.6 to 16.3 mm kV / s. Also, the high-temperature viscosity of the lubricant is characterized by another important indicator: the minimum viscosity at shear rate (106 s-1). For 5w30 oil, this figure is lower (2.9) than for 5w40 oil, for which this figure is (3.50).

Deciphering 5w40 engine oil is quite simple:

1) 5W indicates the low-temperature viscosity of the substance and allows the car to be started at t -35 ° C.

2) We subtract 40 from the figure in front of W. As a result, the resulting number (-35 ° C) will be the minimum oil temperature that will allow the internal combustion engine pump to pump it through the system, ensuring maximum lubrication of the parts.

With such mathematical manipulations, one can easily determine the lowest engine “cranking” temperature. The decoding of 5w30 oil indicates that this parameter is -30 ° C. This is not difficult to determine: we subtract 35 from the value of the engine start temperatures (5 ° C) and it becomes obvious that lowering the oil temperature leads to an increase in its viscosity, and it becomes quite difficult for the starter to crank the engine.

Which engine oil is better 5w30 or 5w40

Engine oil in a car is used for the sole purpose of forming a rich oil film on interacting engine parts. There are very small gaps between such parts in the motor (only a few microns), which require constantly high-quality lubrication. Which brand of lubricant is most suitable for each car, only the manufacturer knows.

Manufacturing companies, recommending the use of a certain type, first of all, take into account the design features of the power unit itself, and already based on these indicators, the characteristics of the oil. Therefore, when choosing an oil, it is recommended to follow the manufacturer's instructions.

It is important to consider that, in addition to the common SAE classification, all lubricants must also comply with the requirements of the API and ACEA systems. Oil marking according to these classification systems is indicated on the packaging, but does not attract the attention of car owners.

As for the popular brands of 5w40 or 5w30 oil:

1) Brand 5w40 effectively holds the film, completely eliminating dry friction of parts. It is ideal for modern units with high thermal stress.

2) Oil marked 5w30 has a much lower viscosity and is indispensable in cold weather, as it makes it easier to start the engine, but in hot weather it becomes too fluid. Under conditions of t 120 - 140 ° C in the engine, the viscosity of 5w40 oil is 50% higher than the viscosity of oil marked 5w30.

Engine oil 5w30 or 5w40 - how to make a choice

It is worth noting that cars with different years of manufacture have their own recommendations regarding the most optimal choice of engine oil. Experts recommend using 5w30 oil if your car is over seven years old and its mileage does not exceed 70,000 kilometers.

If the car's mileage exceeds this figure, 5w40 oil should be filled in, due to the fact that over time, the gaps between the elements that make up the motor increase. Therefore, if an oil with a low viscosity index was previously used, then you should switch to 5w40. In addition to viscosity, these engine oils differ in the amount of additives.

Also, professionals recommend monitoring the reaction of the car to different engine oils. The machine itself will tell you which oil is best suited. For example, on some models of power units, 5w30 oil often does not withstand increased speed (torque), which violates the stability of its operation. To avoid such situations, it is recommended to use the thickest grease in structure.

Oil compatibility 5w30 and 5w40

There are situations when, in the event of a malfunction, it is urgent to add oil to the engine. As a rule, the grease of the exact manufacturer whose product was originally poured into the engine is not always nearby.

The same goes for the viscosity index of the oil, and therefore you should know if oils labeled 5w40 and 5w30 can be mixed. It is worth noting that it is often not recommended to mix an oil with a fully synthetic base oil with mineral oil. It is also not recommended to mix synthetics and semi-synthetics, etc.

As for the grease marked 5W30 / 5W40, theoretically these fluids can be mixed with minimal risk only if they are both products from the same manufacturer. Mixing products from different manufacturers is allowed only in an emergency, but given that they must have the same basic basis.

From this we can conclude that semi-synthetics are mixed only with semi-synthetics, mineral oil is mixed with a similar product, etc. However, it is impossible to unequivocally answer the question of whether it would be possible to add to oil marked 5w40, it would seem, an analogue - 5w30, because for For each type of lubricant, manufacturers use their own additive packages, which, after mixing, can react.

Even if there were no consequences in the event of an emergency topping up of liquids, this is an emergency measure that cannot be used constantly. After the breakdown is eliminated, it is necessary to immediately drain the mixed lubricant from the motor and be sure to change the oil filter, and in some cases it may even be necessary to additionally flush the engine before changing the oil.

Summing up

When choosing engine oil, you have to make a choice of a product of one brand or another, and not only the quality of the engine, but also other significant parts of the car often depends on it. Professionals recommend filling in oil with a higher viscosity, since its use better protects engine parts. 5w30 and 5w40 brand oils are a reliable assistant to a car engine.

Their differences are insignificant, these types of oil are of sufficient quality and meet all European requirements. The use of high-quality oil will protect the power unit of the car from breakdowns and will save on repair or replacement of the motor.