What is the difference between 5w - 30 and 5w - 40 motor oils? Many car enthusiasts are faced with a situation: manufacturers indicate several types automotive fluids applicable for certain brand auto. Therefore, I want to know which of the motor mixtures is better, whether they differ in their properties, because there is a significant difference in price. Let's figure it out.

Marking mixtures according to SAE means:

1. 5w - winter, (the letter w from the English word winter - winter). The cranking temperature is -30 0 C, and the pumping temperature is 35 0 C. These parameters ensure starting the engine without warming up and pumping fluid through the lubrication system.
2. 30 - fluidity index, up to 12.6 mm 2 /s, ensures the formation of a protective film on the motor elements at temperatures up to +20 0 C.
3. 40 - fluidity index, equal to up to 16.3 mm 2 /s, ensures the formation of a protective film on parts power unit at temperatures up to +35 0 C.

These oils are all-season, 5w-40 has a higher viscosity, has a thick consistency and less fluidity.

Oils have different properties due to differences in viscosity, this nuance must be taken into account when choosing them.

Application of fluids for new and old cars.

For cars no older than 3 years, with a mileage of up to 70 thousand km. it is better to fill in 5w - 30. This decision is explained by the presence of gaps between the friction pairs (crankshaft-liner, piston-cylinder). In new cars, the gaps are minimal (measured in microns), they can be filled with oil with low viscosity, which, having formed protective film will protect parts from dry friction.

Long-term use of the machine leads to wear and tear components power unit, increasing the gaps between friction pairs. If the vehicle has traveled more than 100 thousand km, 5w - 40 is filled in. A liquid with a lower viscosity will not be able to provide the required oil film thickness, which will lead to a large amount of oil reaching the combustion chamber and increasing consumption. In contrast, a thick liquid will provide a normal thickness of the protective film.

Characteristics that influence the difference in the thickness of the protective film can be found in the video

How does ambient temperature affect the choice of automotive fluid?

Motor oil 5w - 30 and 5w - 40, what is the difference between their use in summer and winter period? Acceptable working temperature power unit is 86 0 C. At high temperatures outside the car (in summer), or if the car is in a traffic jam for a long time, the engine heats up to 150 0 C. At the same time, the fluidity of the mixture increases, it begins to liquefy (thick - it will change its consistency more slowly, unlike liquid, therefore it can provide reliable operation power unit).

5w - 30 has a lower viscosity, ensures quick engine starting without warming up when sub-zero temperatures. On some models, this fluid does not work well at high speeds; it is better to replace it with a thicker mixture.

Bottom line

Answering the question: “What is the difference between 5w - 30 and 5w - 40 motor oils?”, we compared the characteristics of the liquids and drew conclusions:

1. If the engine is worn out, then pouring low-viscosity synthetics into it is useless.
2. The difference between the viscosity of liquids is one and a half percent.
3. A thin mixture works better in winter, a thick mixture in summer.
4. They differ in their fluidity index at high temperatures.

Choosing motor fluid, take into account the manufacturer's recommendations, technical condition engine, temperature environment(the difference in temperature-viscosity characteristics affects the stability of the motor and the formation of a protective film). Please consult your dealer before purchasing. Buy certified products, the marking 5v - 40, 5v - 30 indicates a fake.

Among synthetic oils Two types of viscosities are popular: oil 5w30 and 5w40. The choice between these two types depends on the mileage of the car. What are the main differences between motor oils and why are they popular among manufacturers of original and non-original oils?

The meaning of the 5W30 and 5W40 markings

Engine oil of 5W30 or 5W40 grades carries information about the viscosity and temperature parameters established for vehicles by the Commonwealth of Motor Transport Engineers (SAE International).

According to the SAE standard, oil can be summer, winter or all-season. Summer oil solutions are marked with a number, for example, SAE 30. Summer solutions are divided into five brands: 20, 30, 40, 50 and 60.

Winter oil fluids have alphanumeric markings, for example, SAE 5W. Letter W, from English word winter means winter. There are six brands winter liquids: 0W, 5W, 10W, 15W, 20W 25W.

All-season lubricating solutions have a combined designation. Such an example would be SAE 5W30 and SAE 5W40 lubricants.

What is the significance of 5W30 and 5W40? The numbers 5, 30 and 40 indicate the temperatures at which the lubricant can be used and viscosity ratings.

The number 5 means that the minimum permissible temperature at which oil fluid can be filled into the engine is -30°. This value is the same for both brands of oils that are being compared, and determines the viscosity of the lubricant when cranking and pumping. The lubricant turning rate will be 6500 MPa, and the pumping rate will be 60000 MPa.

The numbers 30 and 40 are an indicator of the kinematic viscosity of the lubricant at a temperature of +100° and an indicator of the minimum viscosity at a shear rate of 1/1000000 second. Based on the SAE standardization, for grade W30 the kinematic viscosity will range from 9.2 to 12.7 mm sq/s. For brand W40 this value will be from 12.7 to 16.4 mm.sq./s. The shear viscosity of oils for grade W30 will be 2.9 MPa*s, for grade W40 – 3.51 MPa*s.

The standard indicators are not entirely clear to the average car enthusiast. Therefore, let's look at the difference in a simpler version.

Differences between 5W30 and 5W40

Having familiarized yourself with the viscosity-temperature indicators of both oils, it is clear that the main difference between them lies in high-temperature viscosity. The 5W40 oil solution has a viscosity 1.5 times higher than that of 5W30 oil. 5W40 lubricant solution is capable of providing stable operation power plant at higher operating temperatures. Although the remaining characteristics are the same, there are a number of significant differences. They must be taken into account if it is necessary to fill in a particular brand of lubricant:

1. If you use 5W30 instead of 5W40, then there will be more oil. This will create additional load on oil pump. Due to the fact that the viscosity of 5W30 is slightly higher, lubricating fluid may not reach some hard to reach areas. This will lead to early decommissioning of rubbing parts and a general increase in the operating temperature of the power plant.
2. If you choose 5W40 instead of 5W30, the film thickness will become thinner. This will reduce oil consumption, combustion and replacement period. But a thin film on the surface of the pistons and cylinder walls can lead to their rapid wear.
3. The type of oil fluid specified by the manufacturer is very important for the power unit. If the manufacturer's requirements are not met, the motor will be operated in aggressive conditions. This can lead to additional consumption of lubricant, heating and wear of rubbing parts, and failure of the power unit.
4. One of the differences between 5W30 and 5W40 oil solutions is the length of the synthetic chain. The basis for the lubricant is synthetic, which has a certain structural chain. The higher the difference between the temperature coefficients, the longer the synthetic chain, and the shorter the service life of the oil solution.

With such small and insignificant differences, the question of choosing the optimal oil solution for your car always remains.

So, which is preferable - 5W30 or 5W40

The main task of any oil solution is to create an oil film on the rubbing parts of the power unit, ensure its start-up and remove heat. To figure out which engine oil is better, 5W30 or 5W40, you need to make several comparisons. They consist of basic concepts, contradictions and analytical premises:

1. Too small a distance between the rubbing parts of the power unit requires the use of quality oil, which will ensure normal operation of the power mechanism. The most suitable oil fluid for vehicle indicated in the service book by the manufacturer. If the manufacturer recommends the use of 5W30 oil, then you must adhere to this recommendation.
2. The 5W40 oil solution creates a thin and stable film between the rubbing parts, eliminating their contact and friction with each other. It can be perfectly used in power units that have high temperature regime operation. 5W30 is a thicker lubricant and has a lower viscosity. It provides light motor starts in the cold season, but has greater fluidity at high temperatures.
3. Based on its viscosity-temperature characteristics and operating conditions, 5W40 oil fluid must be replaced more often than 5W30.
4. Major passenger vehicle manufacturers recommend 5W40 for their vehicles. If this car is new, or it has a power unit that has been tested major renovation, then 5W30 can be poured into the engine lubrication system. You can make your first run on it from 7 to 10 thousand kilometers. If the car has a high mileage, then it is better to refill with 5W40 lubricant. It will ensure sustainable operation of the salt plant.

When purchasing a canister of oil solution, car owners look at the brand of oil liquid, studying the SAE standard. There are also API and ACEA standards. These are American and European manufacturers Vehicle. They determine the brand of oil fluid that is poured into the power unit, depending on its type, year of manufacture and operating conditions.

The standard of the American Petroleum Institute API has developed 12 brands of oil fluids for gasoline power plants, of which 4 main ones are used:

Brand	Characteristic
S.J.	For installations manufactured after 2001. Oils with improved and additional standards on consumption and energy conservation. Increased stability parameters at high temperatures.
SL	For installations manufactured after 2004. A brand of oil with high energy-saving, detergent and antioxidant properties.
SM	For installations manufactured after 2010. Serves as an analogue and replacement for the SL brand, but with better characteristics.
S.N.	Adopted in 2010 for all types of power plants, including those running on biofuel. Higher requirements for energy saving and wear resistance.

For diesel power plants there are 14 brands of oil solutions, the main ones of which are the last 5:

Brand	Characteristic
CF	For units manufactured after 1994 and equipped with a forced air supply system.
СG-4	For installations manufactured after 1995. A brand with toxicity standards for starters equipped with turbocharging.
CH-4	For installations manufactured after 1995. For high speed diesel starters.
CI-4	For installations manufactured after 2002. Improved CH-4 composition for diesel engines with high sulfur content and exhaust gas recirculation system.
СJ-4	For installations manufactured after 2006, with particulate filters. High antioxidant and stabilizing properties.

If you own a car that has a turbocharged diesel power plant, then the engine lubrication system must be filled with oily liquid SAE 5W40 API CG-4.

ACEA standardization provides for three brands of oils, which have their own categories. These brands are divided into:

1. Oils of grades A and B. They have categories A1/B1, A3/B3, A3/B4, A5/B5.
2. Oils of grade C. They have categories C1, C2, C3, C4.
3. Oils of grade E. They have categories E4, E6, E7, E9.

Based on the type of engine and operating conditions, the driver of the vehicle should know which oil solution is more suitable for his car. If doubt remains or is missing service book, then you can go to the manufacturer’s website and find out what fluid needs to be filled into oil system.

Mixing 5W30 and 5W40

It is not recommended to mix oils that have different synthetic, semi-synthetic or mineral bases.

You can mix oil solutions of 5W30 and 5W40 brands with each other in case of emergency. This is acceptable under one important condition. Both solutions must be from the same manufacturer. After driving for a short time, the mixture must be drained, the lubrication system of the power unit must be flushed and the recommended lubricant must be refilled.

Even though 5W30 and 5W40 are analogues, various additives and additives are used for their manufacture, which, when mixed, form different chemical compositions.

Results

The main difference between 5W30 and 5W40 is their viscosity, and at high temperatures. Therefore, when choosing oils for your favorite car, you need to take into account the manufacturer’s recommendation, the time of year, the condition of the power plant and its operating conditions.

If you live in areas with a warm climate or the power plant has a long service life, then you can fill the oil system with 5W40. In other options, preference may be given to 5W30 oil.

Selection of engine oil is important task for any car enthusiast. The simplest advice for selecting oil is to follow the car manufacturer's advice. But when it is not possible to follow this recommendation, you have to understand the properties of the oil and its labeling.

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

The first number from the motor oil marking 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 motor oil according to widespread SAE classification(American Association of Automotive Engineers). Two numbers in the marking mean that both types of oils are all-season. This versatility is the reason why 5w30 and 5w40 oils are popular among motorists.

Motor oil marking according to SAE classification

Viscosity at low temperatures. This most important property 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 it is for the oil pump to operate. 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 figure reaches 60,000 MPa.

High temperature viscosity. This is the second part of the oil labeling. 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./sec. For lubricant type 5w40 12.6 – 16.3 mm sq./sec. High-temperature viscosity is characterized by another indicator: 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, a thicker film remains on the cylinder walls than when using 5w30. This is the main difference between 5w30 and 5w40, since they behave the same at low temperatures. However, a thicker film is not always a plus.

Marking of 5w30 and 5w40 motor oil on a canister

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

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

Video about the difference between 5w30 and 5w40

Which is better 5w30 or 5w40

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

It should also be taken into account that in addition to the SAE classification, lubricants must also meet the requirements of other systems: ACEA, API. The 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 holds 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 cold weather, but in the heat it becomes too fluid. At a temperature of about 120 - 140 degrees in the engine, the viscosity of 5w40 auto lubricant is 1.5 times higher than that of 5w30.

Winter operation of a car is a difficult test for the engine. AND right choice engine oil often determines how smoothly and safely the winter period will pass for the engine.

In the fall, car enthusiasts often think about what kind of oil better in winter, 5W30 or 5W40? Some say that only the first part of the index, that is, 5W, is responsible for the winter quality of the lubricant.

And since it is the same in both cases, there is no difference between the lubricants. Others disagree and say that much depends not only on winter markings according to SAE. And we will look into how things really are below in all the details.

Features of engine operation in winter

For a more complete understanding of the situation with the choice winter oil, let's try to come from afar. That is, we will understand the processes that occur in the engine during winter operation of the car.

Pumping lubricant through the system with an oil pump

Simultaneously with turning crankshaft starter, the oil pump tends to suck oil from the sump and force it into the line.

The most heavily loaded and critical contacting surfaces in internal combustion engines are lubricated forcibly under pressure (main and connecting rod bearings, piston pins, camshaft beds).

And if the lubricant is too thick, then the pump may simply not create enough pressure to push the oil through narrow lines and distribute it to all rubbing surfaces.

Under such conditions, the engine will not be able to operate for long. The shaft journals and bearings will receive critical damage before the engine warms up and the lubricant flow through the system returns to normal.

Operation of an ultra-thin layer of lubricant in the bearings

If the oil hardens to a plastic state, then it loses its ability to create a so-called oil wedge and normally protect the engine journals.

When trying to start, it often happens that the crankshaft simply does not turn. Many motorists mistakenly believe that the crankshaft counterweights (the so-called cheeks) get stuck in the thick lubricant located in the pan.

In fact, the counterweights in modern engines do not touch the oil in the sump, in principle, never in a calm state, that is, at the time of start-up (if the level is not exceeded).

The cylinder walls are lubricated by oil mist in the crankcase and due to the supply and spraying of oil through the channels in the connecting rods, as well as when it is picked up by counterweights in motion.

It's all about the lubricant frozen to a plastic state between the liners and journals and, accordingly, increasing the resistance to rotation. For older engines, the situation is further aggravated by partial immersion of the cheeks in oil.

Temperature increase in gaps

Here, not only the fact of increasing the gap between the piston and the cylinder and the accompanying breakthrough of hot gases and liquid fuel into the crankcase plays a role, but also the shock loads generated.

The piston no longer sits so tightly in the cylinder, bursting with compression rings, but dangles with a rather large amplitude by the standards of such precisely fitted parts. This will cause avalanche-like wear if the cylinder walls are not promptly and sufficiently lubricated.

In summer, these factors are minimal or absent altogether. The engine is normally protected right from the start if the lubrication is good. Therefore, it is better to approach the choice of oil for the winter thoughtfully and with understanding.

Requirements for oils in winter

It was the peculiarities of winter car operation that necessitated the creation of a system of special requirements for this period. Let's consider only the most basic parameters that are taken into account when assessing winter qualities motor oil.

These are the basic requirements based specifically on the SAE viscosity index. It seems that theoretically there is no difference what to fill the engine with in winter: 5W30 or 5W40.

But in fact there is a difference. It lies in how much the manufacturer has improved the lubrication performance relative to the nominal ones required by the standard.

After all, some oils lack a couple of percent to achieve the 0W index, while others barely reach 5W. And in the first option, oil will be preferable for winter use.

What is the difference between 5W30 or 5W40 oils for winter use

Many motorists mistakenly believe that performance characteristics oils in winter are affected exclusively by the part of the SAE index responsible for winter properties.

This is why they draw the wrong conclusion: Any of the oils in question can be poured into the engine in winter, if the temperature in the region allows.

The so-called summer part of the index (in fact, indicating the operating viscosity at a temperature of 100 °C, which is approximately the same in both summer and winter) also affects the performance of the lubricant in the cold season.

And here, first of all, you need to know the car manufacturer’s requirements for oil. If the documentation for the car indicates that you need to pour lubricant from summer index SAE 40 - pour this oil. If SAE 30 - accordingly, select a lubricant SAE viscosity 5W30.

There are slight deviations from the rules here. If the engine already has a good mileage, and you live in a region with amplitude fluctuations in annual temperature (cold in winter, hot in summer), it is better to take a thicker lubricant according to the summer index.

Example of the difference between 5w30 and 5w40 oil

That is, in winter it is better to pour SAE 5W40, since it may turn out that you will have to drive for a long time on the oil filled in before winter. A thicker lubricant for a motor with wear, due to increased gaps in the friction pairs, is preferable.

What oil parameters, besides viscosity, affect engine performance in winter?

In addition to the SAE viscosity index, motor oil has several other parameters that affect the nature of its operation in the engine in winter.

• Viscosity index (VI). Shows how dependent the oil is on temperature fluctuations. Traditionally, VI is higher for SAE 5W40 lubricants.
• Loss of flow point. Does not apply directly to SAE indicator. Usually indicated on the back of the canister in a table with additional characteristics. Lubricants with a lower pour point will give a greater chance that very coldy The oil will remain fluid and allow the engine to start without problems.
• Type of base and additives used. The better the base and more technologically advanced additives are used to create the oil, the greater the difference between the indices. For example, the vast majority motor oils SAE class 5W40 is synthetic. And 5W30 lubricants are often found in a semi-synthetic version. Synthetics are generally better for any mode of car operation.

A good example differences in oils from the same manufacturer
Brand	SAE class	Kinematic viscosity at 40/100 °C, mm2/s	Density at 15°C, kg/m3	Temperature, °C
				Flashes in an open crucible	Solidification
Shell Helix Ultra VX	5W-30	73,1/11,9	848	200	-39
Shell Helix Ultra AB	5W-30	64,7/11,4	848	204	-42
Shell Helix Ultra AG	5W-30	69,5/11,7	854	230	-36
Shell Helix Ultra	5W-40	72/13,1	853	206	-48
Shell Helix F	5W-40	57,4/9,5	857	192	-45
Shell Helix Plus	5W-40	82,9/14,8	850	230	-36
Shell Helix Diesel Ultra	5W-40	79,5/13,9	854	228	-48
Shell Helix VA Diesel Plus	5W-40	89,1/13,8	856	226	-51

It turns out that, all other things being equal in terms of viscosity, it is better to fill in 5W40 class motor oils in winter. But this is only in the case of approximately the same quality of lubricant.

Summarizing

As is clear from all of the above, the answer to the question of which oil is better to fill in for the winter, 5w30 or 5w40, is complex. Let us briefly collect all the criteria that will help you make your choice.

Automaker requirements

Today, many automakers do not write only one thing suitable oil for all occasions, and give recommendations on selection, which include various conditions car operation.

If, for your climatic region and with your level of engine load, the car manufacturer requires 5W-30 to be filled in, there is no need to neglect its instructions.

If it is possible to use both options, then it is better to fill in more thick oil. This may slightly increase fuel consumption due to increased viscous friction, but will have a much greater impact on fuel consumption. protective properties lubricants

1. Climate. For northern regions, where summer temperature rarely exceeds +20 °C, you can safely pour 5W-30 lubricant if the manufacturer recommends it or allows two options for use.
2. WITH degree of engine wear. For engines with a mileage of more than 300 thousand km, even if this is not indicated in the operating instructions, it would not be a mistake to use oil of higher viscosity. That is, with the recommended class 5W30 according to SAE, you can fill in 5W40.
3. Other oil characteristics. If there are doubts about the choice, for example, for the middle zone, with a relatively new engine and permission from the automaker to use these two viscosity classes in the engine, you need to consider other properties of available motor oils.

Preference should be given to lubricants that have:

• higher viscosity index;
• below pour point;
• higher quality base and technological additive package;
• there are others positive properties, such as energy saving or increased protection of contact patches.

In addition to using high-quality motor oils, the engine life when driving in winter is greatly influenced by the nature of the car's operation.

If you give the engine at least a minimal warm-up before starting to drive, do not spin it up until cold. high speed, change oil and filters on time - problems should not arise after winter operation.

It is impossible to imagine the operation of any rubbing parts without lubrication, the task of which is to reduce wear of mating surfaces and remove heat from the friction zone. Engine internal combustion, installed on most modern cars, like no other mechanism, is sensitive to the characteristics used for its normal functioning lubricants. This is due high speeds rotation of parts and microscopic gaps between parts. Plus, power plants are forced to work in wide range temperatures, which are known to have a significant impact on the properties of materials, including lubricants.

International classification systems provide for the gradation of motor oils according to a number of indicators. The most important among them is the viscosity indicator, regulated by the SAE specification. Currently, some of the most popular oils are those with the designations 5w-30 and 5w-40 defined by this standard. We have already familiarized ourselves in detail with the methods by which the viscosity-temperature properties of lubricants are established. The information provided in that article will be needed to compare the characteristics of the oils in question.

Motor oils 5w30 and 5w40: differences in viscosity-temperature properties

So, the marking of 5w-30 and 5w-40 oils begins with the same index 5w, which indicates low temperature viscosity, affecting cold start engine and its operation at low temperatures. This parameter will not be of interest to us, since it is the same in both cases, which means there are no differences in this part. But the second number is different for the compared oils. It determines high-temperature properties, characterized by two indicators - kinematic viscosity at 100 °C and dynamic viscosity at 150 °C. If we compare the values ​​of these parameters for 5w30 and 5w40 oils, we will find that in the second case it will be greater, i.e. 5w-40 oil is more viscous. In practice, this means that the lubricant has a thicker consistency and, accordingly, less fluidity. In what cases will this be beneficial for the engine, and in what cases will it harm it? We'll figure out.

As is known, the gaps between friction pairs in an engine (for example, crankshaft-liners or piston-cylinder) are measured in thousandths of a millimeter (microns). The exact values ​​are determined by the developers of the power unit. The gaps formed must be filled with a lubricant so as to exclude the possibility of dry friction on some areas of the contacting surfaces. Which oil can do this optimally is known only to the engine manufacturer, who, as a rule, subjects the assembled power units to a lengthy series of tests. Recommendations for the use of lubricants can be found in the vehicle's owner's manual. It is these, and no other, data that the car owner must operate when choosing a specific brand of oil.

What could be the risk of using motor oils that do not meet the requirements? Here everything will depend on whether the oil poured into the engine has a higher or lower viscosity than the recommended one. If oil with a higher high-temperature viscosity is used, then at some engine operating modes the thickness of the film formed between the rubbing parts may not correspond necessary values. IN worst case In some areas, lubricant may not flow at all for a short time. This is fraught with an increase in engine temperature and accelerated wear of parts. On the contrary, using an oil with a lower viscosity does not pose such a threat, since it is more fluid and will therefore quickly fill gaps. If we look at our case, then if there are manufacturer recommendations, it is impossible to use exclusively 5w30 oil and fill in 5w40 oil. Reverse castling can be done, but it is not advisable, otherwise 5w-30 would also be on the list of permitted ones.

Features of seasonal use of 5w30 and 5w40 oils

There is a situation where the manufacturer allows the use of any of the two types of motor oils under consideration, often stipulating that 5w-40 is preferable to use in conditions of high ambient temperatures. What are these recommendations based on? We have already noted that winter operation the designation 5w is responsible, characterizing low-temperature viscosity. Since it is the same for both types of oils, there will be no differences in engine operation at low temperatures. But when the engine gets very hot, certain features occur.

It is no secret to most car enthusiasts that the normal operating temperature of the engine is 86 °C, and deviations from this value are minimal. The readings are taken from a sensor built into the cooling circuit of the power unit, i.e. Engine temperature is nothing more than the temperature of the coolant. It would seem that the oil should not heat up any more. However, in fact, the temperature of engine oil under certain conditions can reach 150 ° C, and one of the factors influencing the maximum value is the outside air temperature. Thus, driving in hot weather at low speeds (standing in a traffic jam) definitely contributes to more intense heating of the engine oil than, for example, driving average speed in cool weather. This is due to less active air flow around the power plant, which promotes cooling. Not by chance SAE specification in terms of high-temperature characteristics, it indicates viscosity values ​​at 100 and 150 °C. Thus, thick 5w-40 oil at higher ambient temperatures in a warm engine acquires a more liquid consistency than in the situation if it were colder “overboard”. This allows it to form a film of the required thickness, which is taken into account by the manufacturer, allowing the possibility of use of this type oils

Use of 5w-30 and 5w-40 oils depending on engine condition

During long-term operation When the vehicle is running, engine parts inevitably wear out, causing the gaps between them to increase. Accordingly, the thickness of the oil “layer” required for friction pairs also becomes larger. Up to a certain point, an increase in clearances does not affect the functioning of the power unit, but sooner or later the wear of parts becomes excessive, significantly exceeding the tolerances established by the manufacturer. In this situation liquid oil, designed for completely different gaps, is not able to form a high-quality protective film in the interface zone of rubbing surfaces, which accelerates their degradation. Another problem could be more oil getting into the combustion chamber and escaping from there. increased consumption. This is exactly the case when filling the engine with 5w-40 oil instead of 5w-30 is a justified step. Its thicker consistency will ensure normal lubrication, but it will not allow it to leak so easily through the increased gaps of the cylinder-piston group or gas distribution mechanism. It is not without reason that after a certain mileage, many car dealers advise switching to oils with increased high-temperature viscosity.

Perhaps this is all we wanted to talk about in this article. We hope that the information presented will be useful in terms of a clearer understanding of the difference between the properties of 5w-30 and 5w-40 motor oils, which influence the choice of one option or another in a particular situation.