If you carefully study all automotive forums, then one of the most common topics is the debate about which oil is better in winter 5w30 or 5w40. This is indeed a topical issue, since those car enthusiasts who are worried about their cars need to have reliable information about which engine oil is best for their engines.

Seasonal characteristics of oils

To figure out which motor lubricant is suitable for winter or summer, you need to turn to its classification, which is established by the Association of American Automobile Manufacturers, for help. Their marking (classification) is based on the viscosity of oils at various temperatures, as well as their ability not to freeze and be fluid so that the oil pump can pump lubricant at sub-zero temperatures and scatter it on rubbing surfaces.

Based on this, motor oils are divided into three categories:

• summer, they have a high viscosity, as they are designed for significant positive ambient temperatures, as well as for strong heating during engine operation, therefore their marking does not contain the Latin letter “w”, but only digital designations, that is, if the tank has the designation 10 w so this brand is designed for winter;
• winter, these lubricants have a lower viscosity, since in cold weather the engine must retain its starting properties, which requires greater fluidity from the oil, so the marking 10w, 5w 20 will indicate that the oils belong to winter driving, so the viscosity of the oil in winter options, much lower than in summer;
• universal (all-weather), these are brands that are produced by manufacturers exclusively for all seasons, that is, the lubricant is ideal for both summer and winter driving, so the 5w20 marking will indicate that the oil is all-weather, unlike grease marked 10 w (winter version) .

Based on the above marking, we can come to an unambiguous conclusion, if there is oil 5 w 30, then it belongs to the all-season, and can be used in summer and winter.

Motor oil manufacturers also produce special additives that can turn the oil into all-weather options, combining summer and winter functions in it. But for such experiments, synthetics are best suited.

Why synthetic. The answer is simple. This oil is produced on the basis of various molecular chemical reactions. Similar manufacturing technology and special additives. Based on this, synthetic lubricants and additives, thanks to similar elements, will be ideally combined with each other.

In this case, the engine will be cleaned of soot and ash, which are formed from the interaction of lubricant and fire in the combustion chamber, if there are backlashes between the cylinders and pistons.

It is important to know that a motor oil test will help determine the lubrication. To do this, just pour part of the purchased product into a glass or other transparent container and wait a few weeks. If the liquid precipitates, then it is not recommended to use such a product for lubricating engine parts. On the contrary, the oil is made of high quality.

Features of engine operation when choosing oil

Having dealt with the marking of motor oils, you can proceed to the performance characteristics of the engine, which affect which lubricant is better to fill in it.

1. Atmospheric temperatures. Despite the technical characteristics of oil viscosity, which are indicated by manufacturers for a particular power unit, they do not always need to be taken into account. Identical power units can be operated at a strong temperature difference, when the oil will not only lose viscosity, but also starting capabilities, or vice versa, when there are no strong differences. Under such conditions, the lubricant will constantly maintain not only starting capabilities, but also viscosity, while maintaining its operating parameters.
2. Mileage . A lot depends on this parameter. No matter how high-quality the motor is, but after certain kilometers, backlash appears in it (the distance between the cylinders and pistons). Based on this, the oil that was previously filled in, and had one viscosity index, will not work.
3. Previously used oil. This is also an important indicator. For cars whose production year exceeds 5-10 years, especially if it is the domestic auto industry, the best motor oil was mineral. It tends to fade quickly, creating ash and soot that accumulates on the walls of parts. Replacing a mineral lubricant with a synthetic product will cause its components to begin to clean the engine, so soot, ash and other solid particles that do not dissolve can clog the oil pump, leading to a loss of lubrication to rubbing parts, and possible engine wedge .
4. Driving style. If the owner of the car likes to drive fast or operates the engine in difficult conditions, then the power unit operates at high speeds. In this case, it is important not to fill it with a lubricant with a low viscosity coefficient. Indeed, with a strong heating of the motor, the oil begins to flow (the protective film decreases), and in fact does not properly lubricate the parts, causing them to heat up and all the ensuing consequences.

Therefore, in order to determine which oil is better for a particular power unit, it is necessary to take into account the above.

It is important to know that lubricant manufacturers invest in the concept of viscosity the ability of the lubricant to form a protective film, which, during engine operation, will protect rubbing surfaces not only from friction, but also from possible chips and microdamages.

What oil is best for the winter

Now you can figure out what to choose for the driver, oil for the winter 5w30 or 5w40, and which one is better.

Consider the characteristics of each of them.

1. 5 w 30 . According to the technical specifications, it is designed for ambient temperatures from -25 to + 25 degrees Celsius. But the number 30 indicates that it has a low viscosity. Based on this, when the engine is very hot, such a lubricant becomes fluid, and can pose a threat to worn motors.
2. 5 w 40 . According to the technical parameters of this oil, it can work effectively at temperatures from -25 to + 35 degrees ambient. Due to the number 40, it has a high viscosity, therefore it can be effectively used in those power units that have traveled a certain number of kilometers (mileage) and have a certain degree of wear.

Based on such technical characteristics, one can come to a certain conclusion about the use of certain oils with different viscosity coefficients.

If the car is operated in the southern and middle latitudes, the year of its release does not exceed 3 years, and the engine life is 70 thousand kilometers, then a good choice of lubricant is oil marked 5 w 30. This is due to the fact that there are no large backlashes in the motor, therefore, even with strong heating and lubricant fluidity , it will form a sufficient ball to protect the rubbing surfaces and ensure the efficient operation of the motor.

The only caveat may be that it is better not to use such a lubricant for those motorists who like to load their engine with high speeds. For such, it is better to choose a product with a high viscosity coefficient.

In that case, when the machine has been in operation for more than 3 years, or its mileage has exceeded 70 - 100 thousand kilometers, then the best oil is products labeled 5 w 40. High viscosity can provide rubbing surfaces with such a ball that will cover not only parts, but also the resulting backlash between cylinders and pistons.

If mineral lubricant was poured into the motor all the time, and then there was a sharp transition to synthetics, or semi-synthetics, then in this case, the chemical additives that make up synthetics or semi-synthetics will begin to clean the motor from various layers in the form of soot or ash, increasing backlash.

If a lubricant with a viscosity of 40 starts to enter the combustion chamber and burn out, this will cause the engine to start “eating” oil. If the lubricant has a viscosity coefficient of 30, then it will be not only in the combustion chamber, but also on the entire surface of the motor.

The worst-case scenario for such an engine cleaning will lead to clogging of the oil system, and at one fine moment, the liquid will stop being supplied to the rubbing surfaces, causing the motor wedge.

Therefore, advice to motorists who drive used cars is that when changing the oil, the engine should be well washed in a service station.

Summing up all of the above, we can come to the following conclusion. The best all-weather lubricants for engines, which have low mileage, must have a viscosity coefficient not exceeding the number 30. Otherwise, there will be a loss of power and high fuel consumption.

In those power units that have high mileage, or have worked out a significant part of their motor resource, it is better to fill in engine oil with a viscosity coefficient equal to the number 40. Such a lubricant can compensate for existing backlash in the motor.

It is important to know that oil manufacturers currently produce special additives that can increase or decrease the viscosity index of any oil.

In order to choose a lubricant for winter driving, the driver must be guided not only by the viscosity coefficient and the marking of engine oil. He is also obliged to take into account the technical condition of his motor, as well as the climatic conditions of the vehicle.

Despite the scheduled maintenance work, which includes changing the oil in the internal combustion engine upon reaching a certain mileage or after a year of operation. Some car enthusiasts and professionals prefer to perform a seasonal shift. Motorists explain the double replacement by a high temperature difference in the summer and winter periods of operation.

When preparing for winter operation, the question arises: “Which oil is better than 5w30 or 5w40?”.

What is the difference between 5w40 oil and 5w30

To understand how 5w40 oil differs from 5w30, you need to understand the meaning of the numbers and letters in the marking. Firstly, this is a generally accepted designation that indicates the temperature conditions and viscosity of the technical fluid according to the standards adopted by the International Association of Automotive Engineers (SAE).

When choosing a product, it should be borne in mind that SAE is not the name of a manufacturer, but only the name of a single international standard that promotes engine oils from various companies.

Deciphering these four characters in the designation will allow you to decide what is best to pour into the engine for its winter operation. A good definition with a choice is indicated in the car's instruction manual. This book, which comes with all new cars, is more specific about what to put in the crankcase and makes it easy to choose between 5w40 and 5w30, and sometimes no choice.

So, the first group of numbers, which can have a value of 0, 5, 10, 15 and 20, means the temperature regime at which the engine can be started. The letter W means that the temperature regime is determined for winter operation. The second group of numbers means the maximum outdoor temperature at which the contents of the canister retain their properties.

Accordingly, the difference between 5w30 and 5w40 lies in the possibility of summer operation of the oil.

The main difference lies in the chemical composition of the oil. The basic basis for 5w30 or 5w40 oils from the same manufacturer is the same.

The physical properties of the finished commercial product are changed by the use of various additives that affect the state of the contacting liquid film between the rubbing parts at different temperatures.

5w30 or 5w40 oil has additives that prevent rubbing parts from seizing at temperatures down to -30C.

5w30 or 5w40

The use of 5w30 or 5w40 oil is determined by the climatic characteristics of the region where the car is mainly used.

Oil operation during winter operation

There is no difference between oils in terms of winter operation. The decoding of the designation shows that both options under consideration behave perfectly when starting the engine up to a temperature of -30C. And retain their lubricating properties when operating at such low temperatures.

At the time of starting the engine, many systems are included in the work. The mating parts, when in contact at the moment of starting, create sufficient resistance, and therefore the winter mode requires a sufficiently powerful battery to drive the entire mechanism.

5w30 and 5w40 are designed to start the engine at temperatures not lower than -30C. Within these temperature limits, the manufacturer guarantees that the friction force generated in the mating surfaces will remain acceptable and will not go beyond the technical parameters laid down by the engine designer.

Operation of these oils at lower temperatures is also possible. When starting at lower temperatures, keep in mind that the liquid will be thicker and a more powerful source of electricity will be required to start the engine, capable of cranking the engine.

An oily liquid with a winter index of 5 has a freezing temperature from -45 to -55C. It should be noted that this indicator has little to do with the extreme low temperatures of the launch. At a temperature of about -35C, phenomena occur that affect the operational reliability of the engine as a whole. A so-called "oil wedge" appears in the mating parts.

The liquid ceases to be fluid, but passes into a gel-like form of a grease close to the state, which has an increased coefficient of friction. When starting the engine at such low temperatures, it does not matter at all which of these two oils is filled with 5w30 or 5w40, their characteristics cannot differ at low temperatures.

Oil operation during summer operation.

When starting the engine in summer at high temperatures, viscosity parameters are also important. If it is too liquid, and not designed to work at high temperatures, then thinning of the film is possible, which will lead to a general oil starvation of the engine, and will affect the increased wear of the moving parts of the unit.

For summer operation, a thicker oil is desirable, which has a higher viscosity and better lubricating properties. A liquid lubricant designed for high summer temperatures does not allow the formation of a phase of sufficient viscosity to run off the upper surfaces of the parts and flow out from the bottom of the mating pairs.

Engine oil 5w30 and 5w40 what is the difference in summer operation? At summer air temperatures not exceeding +30C, there is no difference. Both lubricating fluids work in the same way and have all the declared properties. If the temperature exceeds + 30C, while not crossing the threshold value of + 35C, then it is preferable to use 5w40.

This small difference does not greatly affect the final results of operation. The fact is that in the summer the engine warms up very quickly and reaches operating temperatures. Immediately after starting the engine, the oil pump is turned on, which provides a supply of lubricant under pressure. Therefore, starvation of the engine is possible only in the first seconds of engine operation.

This feature of the summer operation of the internal combustion engine must be taken into account when the engine is frequently started in the parking lot in order to turn on the air conditioner. The economic benefit of saving fuel can be negated by the cost of troubleshooting.

The work of oils during engine overheating.

When overheated above 90C, even by 10 degrees, the physico-chemical properties of the lubricant can change. With such overheating, accelerated oil oxidation occurs, which reduces its overall service life. When the engine “boils”, it is necessary to change the oil as soon as possible. This is especially true for mineral and semi-synthetic bases.

For synthetic oils 5w30 or 5w40, overheating is not particularly terrible. Synthetic oil, due to the available additives and synthetic base, is not subject to oxidation during the entire service life, provided that the critical temperature of 150C is not reached. Therefore, a synthetic-based lubricant is recommended for use in engines that experience increased loads.

This is especially true for light trucks, which often operate in excess of the passport commercial load.

Oil for the winter

So which oil is better 5w30 or 5w40 in winter? From the point of view of winter operation, there is no difference. Since this type of oil is universal and suitable for all-weather use, when choosing a specific brand for viscosity, it is necessary to focus on summer temperature indicators.

With an average annual mileage of more than 30,000 km and an oil change exclusively for winter operation, it is more rational to use 5w30 standard oils from an economic point of view. If we take one manufacturer, then the difference in the cost of a liter package with different numbers in the second designation group can be from 80 to 150 rubles.

With an average annual mileage close to 15,000 km, which corresponds to the oil change interval for modern engines, it is more preferable to use oils of the 5w40 type for the winter, as it has higher lubricating properties at temperatures above + 30 ° C in the summer, which can be understood when deciphering the code.

Many car owners, when it is necessary to change the oil, have a lot of questions, because they don’t know exactly the nuances of choice and application. Most often, you should not deviate from the recommendations of the vehicle manufacturer. This solution is the most optimal for the safety of the functions of the car. The search for the ideal remedy is considered one of the most important processes. Many motorists are interested in figuring out which one is 5w30 or 5w40. There are many opinions on this topic, this article will help you figure it out.

What is the difference between 5W-30 and 5W-40 oils.

What is conditional marking 5w30 and 5w40

These synthetic motor oils come in an affordable price range and are well suited for use in many vehicles. Deciphering oil 5w30 and 5w40:

1. The first digit indicates the speed of movement of the product at a high temperature of the motor.
2. The letter W - "Winter" (translated from English as "winter") indicates the possible use of the tool in the northern latitudes.
3. The last digits indicate low temperature viscosity. 30 or 40 are subtracted from the number 5, thus, the temperature at which a cold engine is allowed to start is -25 and -35 degrees, respectively.

What is the difference between 5w30 and 5w40 oils

Before you buy or 5w40, you need to figure out what is the difference between them. Lubricants are characterized by identical indicators indicating suitability for winter use. But you should pay attention to the high temperature viscosity according to SAE - this is how it differs from 5w30. So, the kinetic viscosity when heated to 100 degrees will be (mm kV / s):

• in the "thirty" 9.3 - 12.5;
• in the "magpie" 12.5 - 16.3.

Both varieties are characterized by a minimum HTHS viscosity of 2.9, but in the "magpie" the figure can reach 3.7. Based on the above, you can determine which oil is thinner. In this, 5w40 is superior to its counterpart.

Which is better: 5w30 or 5w40

Experts, discussing the topic of which oil is better in winter - 5w30 or 5w40, advise starting from the brand of car, its age and climatic conditions in which it has to be operated. It is believed that if the car was released a couple of years ago and did not have time to go 70 thousand km, it is better to fill in the “thirty”. If the mileage of the car has reached 100 thousand km. and more, means . This is due to the increase in the gaps between the rubbing parts. Consequently, the lubricant will drain through them much faster, so in this case, low viscosity will become a disadvantage.

Experts note that it is better to pour a substance with the designation 5W40 into improved internal combustion engines, which are characterized by high thermal stress. This lubricant retains its viscosity properties well and allows you to create a protective film, eliminating the risk of unforeseen situations. It is necessary to choose the oil carefully, focusing on a large number of decisive factors. It is better not to deviate from the manufacturer's advice, since the risk of damaging the constituent elements is quite large.

Oil compatibility 5w30 and 5w40

Many motorists are interested in 5W30 and 5W40. Often this is necessary in the event of a malfunction, when you need to top up the motor substance. When during this period the necessary substance previously used for the power unit is not at hand, this issue is particularly acute. Experts do not recommend mixing mineral oil with a variety that has a synthetic base. It is not advised to mix synthetics with semi-synthetics. Mixing of these oils is allowed only if they are made by the same manufacturer, and also if they are made on the same basic basis. Then the risk will be minimal.

No one can definitely say whether it is allowed to add 5W30 to 5W40 or vice versa. Doubts lie in the fact that each variety has a special set of additives that can react after mixing. Even if there are no negative consequences, then it is still not worth the risk in the future. After fixing the breakdown, you will need to immediately drain the product, change the oil filter, and sometimes flush the motor itself.

The choice of lubricant for the motor is an individual decision. But the main rule for operating a worn motor is to increase the viscosity of the oil. If you previously purchased a “thirty” substance, then now you need to give preference to 40, then replace it with 50. Due to the increase in viscosity, the intensity of friction of car parts decreases, and their wear resistance improves.

The extended temperature range of 5W30 and 5W40 oils has made them popular with Russian car owners. Why? What benefit will the engine get from this, which oil is better: 5W30 or 5W40 in winter?

Synthetics or semi-synthetics

There is currently a trend towards a wider range of viscosities. Chemists have made the most significant steps in this direction in relation to the creation of synthetics, adding more and more new components there. For example, Mobil, which was the first to bring a synthetic lubricant to the market, has been working with it and experimenting for over thirty years. A huge number of emerging competitors are also on the alert and spend huge amounts of money to create a new product with advanced features. But there are few developers producing highly specialized synthetics, for example, for highly loaded diesel engines.

In addition to "five" - ​​synthetics, there is a similar semi-synthetics. Why not use it? Of course, you can also use liquid mineral water, add thickeners there, a synthetic component with a modern set of additives - and you get a completely standard semi-synthetic in winter, for example. However, it is known that its parameters in any case will be lower compared to synthetics. After all, the oil base plays an extremely important role, setting the physico-chemical base.

A well-known analogy can be traced with gasoline. There is a technology by which a lot of additives are added to low-octane A-80 gasoline in an artisanal way and AI-98 is obtained. But, having worked on such fuel, the engine will soon require repair: at least it will be necessary to flush the injector and replace the spark plugs. After all, it is quite clear that full-fledged gasoline of the highest quality will be obtained only through the use of appropriate technologies.

Viscosity

This characteristic is of paramount importance for a lubricating fluid. This parameter defines the maximum oil application temperature. Therefore, which oil is better: 5W30 or 5W40 (winter or summer) is determined precisely by this parameter. If the indicator is low, the lubricant should not be too viscous to cold start the motor with a starter and pump it through the pump. In high-temperature conditions, the oil, on the contrary, should not have too low a viscosity in order to be able to maintain a constant required level of pressure in the system and form a film that protects against friction around the parts.

So, they are divided into:

Winter. With a low viscosity, the engine will start easily, but the lubricant will not work effectively at high temperatures.

Summer. Cold start will be problematic at temperatures below zero degrees, however, with high viscosity, the motor will be reliably and stably lubricated in warm and hot weather.

All season. When it's cold outside, the oil exhibits the quality of winter lubrication, and when it's hot - summer.

All seasons are becoming more common, replacing the first two types, since now there is no need to change the oil every time the season changes. At the same time, they show themselves to be more efficient and energy-saving. An example of such a lubricant is 5W40 oil (synthetic).

Other characteristics

Of course, other characteristics are also important for oil: detergent, antiwear, anticorrosion and antioxidant (additives are used for this). However, viscosity is one of the main values. Many modern additives increase the price. Therefore, you should always pay attention to this parameter and choose the optimal ratio of lubricant properties and future engine operating conditions.

The main prescription that should be followed when choosing is the requirements of the vehicle manufacturer. They are listed in the user manual. Typically, they not only contain information about the specific properties that should be inherent in the lubricant used, but also offer specific brands of oils with recommendations for using them. Shell oil (5W40, 5W30 or other type) is often found in the manual. At the same time, if your car is far from new, and you have little information about its operation, then you can choose the brand for the engine or transmission yourself.

1999 SAE Standard

What do those cryptic SAE letters stand for? From English, the abbreviation translates as "Society of Automobile Engineers" (Society of Automobile Engineers). This is an international standard that viscosity must comply with. For example, in 1999 the requirements of the standard were as follows.

According to the oils, they determine the correspondence to a certain season. It is calculated at low speeds from twenty to one hundred degrees and separately at one hundred degrees.

Starting properties are revealed through resistance at and the possibility of obtaining revolutions. Depending on the viscosity and class, they are determined at temperatures from ten to thirty-five degrees below zero and high shear rates (105s-1), that is, the conditions for working in crankshaft bearings during cold start are considered.

Pumpability determines the rate of passage of lubricant to rubbing parts during a cold start, as well as the possible risk of engine breakdown during a cold start due to the rotation of the liners. The indicator is considered at negative temperatures from fifteen to forty degrees and at low shear rates (10s-1). Under these conditions, the lubricant spreads in the sump to the oil receiver when starting a cold engine.

Viscosity at high temperature reveals the real indicator during operation of highly loaded motors in the warm season. Thus, anti-wear characteristics, losses due to friction and the impact on the efficiency of the motor are visible. It is fixed at high shear rates (106s-1). Under these conditions, the crankshaft bearings operate under high temperature and load.

SAE classification

This is the SAE specification, which determines in various conditions. There are currently six winter classes and five summer classes. Winter is easy to identify by the presence of the letter W (“winter”, which means “winter” in English). The higher the viscosity, the larger the numerical index will be.

Winter viscosity is indicated by 0W, 5W, 10W, 15W, 20W. 25W.

Summer - 20, 30, 40, 50.

Consider 5W40 oil as an example.

Its characteristics are as follows. Class - viscosity 5W. As you know, it can be used in the winter, that is, it depends on this indicator how easy it will be to start the engine in the cold. Thus, in order to understand which oil to fill in in winter, you need to pay attention to this particular indicator.

The number "40" reveals summer performance, that is, the ability of the engine to operate at high temperatures.

If, as in our example, there is a designation of both one and the other classes (that is, motor oil 5W40, as well as 5W30), this indicates the all-weather nature of its use.

How to choose a winter class

When choosing a viscosity, they are primarily guided by the instructions of the car manufacturer. If there are none, follow the general recommendations.

When choosing the best oil for winter, you need to take into account the conditions under which the vehicle will be operated.

Then problems with starting in winter and negative consequences for the motor (for example, rapid wear and jamming at startup, which can occur under oil starvation conditions) can be avoided regardless of whether you have 5W30 or 5W40 filled in for the winter. It must be understood that when starting the engine, even if this does not happen in severe frost, but with a positive mark on the thermometer, it takes time for the oil pump to pump through the lubrication system so that the liquid enters all rubbing parts and channels. Until this time, the engine has been running in conditions of lack of oil. Therefore, friction and wear are greatly increased. The more the lubricant can keep fluid in low temperature conditions, the better the protection for the motor will be provided.

How to choose an all season

Winter properties are displayed on the left side, and summer properties are displayed on the right. Thus, wondering which oil is better - 5W30 or 5W40 - in winter, you need to pay attention only to the indicator on the left, and in this case it is the same.

Therefore, you should pay attention to the difference in summer mode and select the appropriate option depending on the operating conditions of the vehicle.

Viscosity-temperature properties

Ensuring the engine start without heating, free pumping of oil through the system and, as a result, stable lubrication of all rubbing parts at the maximum possible loads and ambient temperature depends on this indicator.

Even in a temperate climate, the change in winter temperature to the greatest warming up is up to one hundred and ninety degrees. Therefore, seasonal oils must be changed depending on the time of year. However, with the advent of all-weather seasons (they include, for example, motor oil 5W40 and 5W30), the problem was removed. Thanks to their additives, they are able to exhibit the required properties at various temperatures. That is, with a negative value, they are like winter oils, and with high positive values, they are like summer oils.

Additives

Additives do not greatly increase the viscosity at low temperatures, but they increase it strongly at high temperatures, when the number of macropolymer molecules increases significantly. In all seasons (which include 5W30 grease and 5W40 oil), the characteristics lie in the temporary possibility of changing its viscosity, also relative to shear rate. When the speed decreases, it increases, and when it increases, it decreases.

Most of all, this property is manifested at low temperatures, but it is also preserved at high temperatures, which has good consequences for the engine: low viscosity when the engine is cold makes it easier to descend, and when it is warm, energy loss due to friction is reduced, thereby saving fuel.

Low temperature

The low temperature characteristic of an oil is revealed through the pour point when the lubricant stops flowing. This indicator is realized when the temperature is five to seven degrees below that at which fluidity was possible.

Most often, solidification occurs due to the formation of paraffins in the chilled lubricant.

Which oil is better: 5W30 or 5W40 (in winter)

Based on the foregoing, it is clear that in the cold season, both species manifest themselves in the same way. Therefore, both one and the other type of lubricating fluid are perfect for winter.

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.