Why engine oil turns black quickly: reasons, black engine oil. Why engine oil turns dark quickly Why is it black after an oil change

14.10.2019

The fact that over time, engine oil becomes dark, most motorists take it for granted. Much more controversy can be found on the network when it comes to too fast. Opinions differ greatly here - some argue that there is nothing to worry about, especially if the power unit is old, others believe that this is a sign of an impending disaster that requires an immediate response. We will try to describe this problem in as much detail as possible, using a multi-aspect approach - this way the reader will have a more objective opinion about the problem.

Why does the oil darken

To begin with, let's try to figure out how MM works in general in a power unit. It is intuitively clear that this fluid is used to prevent premature wear of the rubbing surfaces of engine parts. But this is not the only function of the oil: it also acts as an adsorbent that cleans the surfaces of the engine from technical contaminants that are inevitable during the operation of the car. Since engine oil itself does not have adsorbing properties, special additives are introduced into it that change the base number of the liquid.

Black oil in the engine indicates that the alkali still performs its functions - it neutralizes acids, and also rids the engine of carbon deposits and other pollutants. Since the lubrication system is by definition sealed, all this dirt ends up in the lubricating fluid. Partially, it settles on the oil filter, but it is not able to catch the smallest particles. So the color of the oil quickly changes to a darker one, and the more worn out the power unit, the more clearly this dependence manifests itself.

But when the lubricant retains its color for a long time - this is already a reason to think, but does it cope with its cleaning duties? Most likely not, which means that either you deliberately purchased cheap oil of dubious quality, or you came across a fake, of which there are a dime a dozen on the market today. Due to the lack of high-quality additives, such a liquid performs only lubricating functions. And those, most likely, are by no means properly.

The “correct” oil has a sufficient base number, which helps prevent two main causes of premature wear of the power unit:

oil deficiency, which is the result of clogging of channels with contaminants that prevent the normal circulation of fluid;
deterioration of heat dissipation, the consequence of which is overheating of the motor with all the ensuing negative consequences. In particular, local overheating causes the liners to rotate, deformation and destruction of the camshaft, and other equally dangerous consequences.

But not everything is so clear. A high alkaline number, it turns out, in certain cases, instead of good, brings tangible harm. Under such cases, first of all, one should understand ignoring the scheduled replacement of lubricants. With prolonged use, the adsorption additive, resisting the heavy contamination of the motor, gradually loses its cleansing properties.

So the darkening of the color of an initially light and transparent product should not be surprising: this is a natural process. In some cases, the oil in the engine turns black quickly, sometimes for quite a long time, but in any case, the color changes to a darker one. The speed of the process initially says little, since it depends on many diverse factors, the main of which are:

the condition of the motor, how regularly routine procedures were performed;
what is the concentration of detergent additives in the currently used product;
how long ago did you change the MM and oil filter.

The older the power unit, the more various deposits have accumulated in it, therefore, after filling in fresh fluid, it darkens faster than on a relatively new motor. The rate of color change directly depends on the amount of alkaline additives, which in different brands of oils can differ by a noticeable amount.

The faster darkening of engine oil in a diesel engine is associated with the characteristics of diesel fuel, which contains many more substances that generate soot during combustion. For this reason, on such engines, the oil turns black almost immediately, and this fact should be known to every owner of a car with a diesel power unit.

If you are convinced that the speed of the process is too high, you have two ways to perform an experiment that will help establish the truth:

the use of more, the quality of which can be no doubt;
more frequent replacement of the lubricant (about 20-30% more often than recommended by the automaker).

But such a step should be taken only in cases where the contamination of the lubricant is not critical, that is, it does not create problems that threaten the state of the power unit. But when this process is accompanied by engine malfunctions, you should first perform a thorough diagnosis of all its systems and components, which will indicate the possible cause of the rapid contamination of the technical fluid.

You can try to reduce the rate of contamination of the lubricating fluid by flushing the motor with special mixtures that are able to clean the internal surfaces of the engine from those deposits that the oil cannot cope with. But one cannot overdo it here, since such compounds have a destructive effect on rubber parts and seals. In addition, it is impossible to predict in advance the reaction of the base lubricant to mixing with a cleaning solution - in a negative scenario, the MM will lose a significant part of its characteristics.

We list the factors that have the greatest influence on the rate of darkening of engine oil:

crankcase gases entering the engine. Problems in the system for getting rid of crankcase gases lead to the fact that some of them penetrate back into the CPG, where they can come into contact with engine oil. As a result, the lubricant oxidizes, losing its performance characteristics and quickly changing color to dark. If the malfunction is significant, the speed of this process increases rapidly;
piston group wear. The main consequence of this phenomenon is the loss of tightness of the CPG, as a result of which lubricant begins to enter the combustion chamber, which should not be there, and fuel enters the crankcase of the power unit, diluting the lubricating technical fluid. The oil eventually loses its original lubricating and cleaning properties, increasing the wear of rubbing parts and its own pollution. Diagnosing such a problem is quite simple: you just need to wipe the oil dipstick with a clean, light rag. The presence of saturated black streaks will indicate such a phenomenon as the waste of lubricant resulting from its combustion in the cylinders. With an increase in gaps due to engine wear, one can observe an increased consumption of MM, and problems with starting the engine, and a high degree of exhaust smoke;
high ash content and TBN. Sulphated ash content is an indicator that characterizes the quantitative content of elements in the oil that do not burn. It directly correlates with the base number, abbreviated as TBN. This means that the higher the ash content, the faster the lubricant will darken during operation. This cannot be called a disadvantage - high washing abilities are only welcome, however, when choosing an oil, you should focus on the indicators recommended by the automaker, trying not to exceed them unnecessarily. It must also be understood that a lubricant with a low alkalinity index is very sensitive to fuel quality and loses its cleaning properties faster. For this reason, the replacement of such a MM should be done much more often - approximately every 7-7.5 thousand kilometers;
overheating of the motor is another reason why the oil in the engine darkens much faster. Such consequences are caused by the operation of the car in an aggressive mode with prolonged increased loads. The cause of overheating may be a coolant leak, as well as a malfunction of the thermostat or water pump, the occurrence of air plugs in the cooling system line.

Note that all of the above reasons are associated with certain malfunctions of the engine or its systems. Therefore, too rapid darkening of the oil is a reason to contact a service center to diagnose the power unit. If the warranty period has already expired, with sufficient experience, this work can be done independently.

When dark oil is the norm

The automotive lubrication system is a closed sealed circuit. Draining into the crankcase, the oil is then pumped to the main channels passing through the lubricated parts. Along the way, it absorbs oxides, mechanical particles formed during friction, as well as soot, and returns to the crankcase. It is not surprising that it, constantly enriched with various pollutants, darkens.

Since the parts of the power unit operating at extreme speeds are very hot, a significant part of the heat is transferred to the technical fluids - antifreeze and engine oil. The latter can be heated to temperatures exceeding 100°C. This is good for lubrication - it becomes more fluid, which allows it to penetrate technical gaps, reducing friction and washing away fresh carbon deposits that have not had time to coke. This natural darkening is termed "oil work".

So if, after prolonged use, the MM has practically not changed its color, they say that the lubricant does not work. At least, it concerns its cleansing characteristics. In this case, all deposits remain on the walls of the motor, forming a rather thick layer of indelible soot, which, firstly, changes the size of technological gaps and the geometry of engine components, and secondly, worsens the heat transfer of the power unit, which leads to prolonged operation at elevated temperatures . Figuratively speaking - to overheating. Consequently, the car owner uses a frankly low-quality product, a fake that reduces the life of the motor.

Black oil in the engine is not a cause for concern if the dark color is acquired gradually over the scheduled interval. Thus, if the lubricating fluid after hitting 5000-10000 kilometers generally retained its original performance, but darkened - this is normal, this is an indicator that the oil used is suitable for a particular engine.

If the oil in the engine turns black, this only indicates that all pollutants, including the compounds used during the combustion of fuel assemblies, enter the lubricating fluid without lingering on the walls of the working area. This protective ability of engine oil minimizes the likelihood of oxidative reactions inside the power unit, increasing its resource. During the scheduled maintenance at the next maintenance, all the substances washed out by the lubricant are drained, and clean oil is poured into the system.

Gradual cleaning of the engine

As we found out, the change in the shade of the oil is the result of the ingress of pollutants into it, which are formed in the engine during its intensive operation. High-alkaline additives also contribute. A color that is too dark does not at all mean that there are problems with the power unit, this is a completely normal natural process, but with a strong darkening of the MM, it should be replaced along with the oil filter, without waiting for the numbers corresponding to those given in the instruction manual to appear on the speedometer. If your goal is to gradually clean the engine of accumulated contaminants, change the oil filter not only when changing the oil, but also in between, at least once. This is not such a costly way to not try to use it.

It is safe to say that the slow cleaning of the engine from suspended microparticles is much more useful than the express method based on the use of detergent additives with aggressive components, which, as a result of mixing with oil, worsen its technical parameters (in particular, viscosity).

A more fluid lubricant flows into the sump faster, without lingering in the working areas, which causes faster wear of motor components that need high-quality lubrication.

Many car owners refuse the gradual cleaning method, considering it too expensive. In fact, a more frequent replacement of the MM will initially lead to the fact that over time it will become contaminated much more slowly, returning to the indicators that were observed in the days of the youth of the power unit.

For old, heavily worn engines, one of the most typical causes of accelerated darkening of the lubricant is the ingress of combustion products into the oil, that is, crankcase gases. Such a problem is easily diagnosed, since this process is accompanied by the appearance in the engine compartment of a very specific and recognizable smell of burnt MM. This will also be evidenced by an increase in its consumption, as well as an increase in fuel consumption.

The problem is treated by replacing the piston rings, and in especially severe cases - boring sleeves, which allows you to give them the original standard dimensions.

Another good way to prevent premature contamination of the lubricant is to regularly top up with a decrease in level until it is time for a scheduled change.

Most experienced car owners claim that when using high-quality lubricating fluid, it begins to darken after fairly significant runs, about 7-10 thousand kilometers. If the initial alkalinity is high, when such an oil darkens, no destructive processes occur in the engine. The dark color in this case is evidence that the lubricant managed to absorb the maximum amount of harmful deposits accumulated on the surface of the motor parts. You should not rush to replace, perform this event in accordance with the recommended dates.

At the same time, in the specialized literature, one can find information stating that motor oils with a high content of alkaline additives are characterized by a shorter resource, which is due to the absence of components in their composition that prevent the aging of the working substance. For the excellent washing characteristics of such liquids, you need to pay with more frequent replacement. The optimal mileage is considered to be at the level of 10,000 kilometers.

Consequences of long driving on black oil

The roots of the misconception of many motorists regarding the color of MM, which manifests itself in the form of rejection of the black color of the lubricant, should be sought in the Soviet past, when the quality of the oil was directly associated with its color, and this was true. But it was a long time ago. Today, even a frank fake has a transparent consistency and a light shade.

If, after long-term operation of the engine, the oil darkens slightly, this indicates either that the engine is not very dirty, or that the alkalinity is not high enough. In the latter case, the lubricating properties of the liquid do not suffer in any way, but the cleansing properties are frankly insufficient.

Dark MM indicates that it regularly performs cleaning functions, but the functionality of such a lubricant is sharply reduced. If you continue to drive on such an oil, it will no longer be able to wash off the pollution products from the surface of the parts of the power unit, contributing to the thickening of the soot layer on key engine components.

Prevention measures

It is possible to avoid the consequences of too rapid contamination of the lubricating fluid, but the task is complicated due to the fact that the reasons for this phenomenon can be different.

- this is the basis on which such an indicator as the durability of the engine is based. In principle, the user manual indicates the main characteristics of the liquid, which must be strictly adhered to. Any initiative inspired by the advice of "experts", including store ones, can lead to not too good consequences. If you see that the lubricant is quickly darkening, do not reuse the same oil, since in this case it will be much more difficult to establish the cause of the phenomenon.

Liquids with low alkalinity for older engines are definitely not recommended, even if they are quite suitable for your engine in terms of basic characteristics. In this case, a thorough study of the technical documentation, including the specifications of a particular ICE model, will help you find the best option. A lot of useful information can be gleaned from thematic forums and social network groups, but here you need to be able to distinguish competent material from amateur material, and this is also a kind of art that comes with experience.

The second effective way to avoid adverse consequences is to repair the power plant. As we wrote above, it is very likely that the cause of accelerated contamination of motor lubricant may not be in its performance, but in engine malfunctions. Diagnostics and repair - a recipe for "recovery" of the motor. It is not in our plans to describe the features of the first and second procedures, there are enough materials on the network on this subject, and on our website you can find a lot of interesting and informative. In particular, how thermostat and pump breakdowns are diagnosed and corrected, how the degree of wear of the piston group is determined.

It remains only to add that all these problems can be fixed on your own, using at least the same instruction manual, which usually sets out the main breakdowns and provides an algorithm for their elimination with a fairly detailed description with pictures.

If you do not have experience repairing a car, then it remains to turn to specialists and put up with tangible cash costs.

One of the standard procedures that used to be regularly performed, but today they prefer not to use it, is flushing the engine during the next oil change. It is especially useful if you change the brand of lubricant. Usually, both the oil change and the engine flush are carried out at the service station, but if you are used to changing the MM yourself, then you can certainly handle the cleaning procedures.

To do this, you will need the following tools and supplies:

wrench for unscrewing the drain plug located on the bottom of the crankcase. Its configuration depends on the specific car model,
a container of sufficient volume to collect mining;
flushing fluid (it is advisable to choose the same brand as the engine oil, but not necessarily - you can use any other, but from a well-known brand).

How is flushing done:

install the car on a pit, lift or overpass;
find a drain hole from the bottom side and unscrew the plug, after substituting the prepared container (this work must not be done on a hot engine - there is a risk of burns);
wait until the oil stops dripping. Note that the completely cooled oil becomes more viscous, and we do not need it - the thinner it is, the more completely it will merge. Considering the previous advice, we recommend waiting 10-15 minutes after a long trip, and only then proceed to the drain, which can be considered completed 20-30 minutes after the start;
screw the drain plug back into place, open the hood cover and unscrew the filler plug, if any (or remove the dipstick if its neck is a filler);
it is necessary to fill in the system exactly the same volume of flushing liquid, which turned out to be drained;
screw the plug or insert the probe into place - everything is ready for flushing;
you just have to drive a car about 20-50 kilometers. Less is not worth it, more is also undesirable, because the flushing agent does not have as good lubricating characteristics as regular motor oil;
after that, the flush can be drained. If the engine is very dirty, the drained fluid will have a glossy black color, and this is a good sign indicating that the special tool did its job perfectly. If you want to get an even better result, repeat the procedure;

Credit 6.5% / Installment / Trade-in / 98% approval / Gifts in the salon

Mas Motors

For many owners of different brands of cars, it is a mystery why the engine oil quickly darkens. There are several reasons that lead to this result. We will figure out what caused the rapid darkening of the oil, and then we will find out whether it is dangerous for the car or not.

Reasons for the rapid darkening of the oil in the engine

During operation of the motor, the oil gradually changes its color and becomes darker, and sometimes black. For many, this is intimidating and intimidating. In fact, oil blackening is a natural process. Sometimes it goes faster, sometimes slower. But why is it happening at all? Due to the following reasons:

there is little alkaline additive in the lubricant;
the piston group is worn out, due to which a large amount of combustion products and fuel oxidation enters the lubricant;
the motor overheats, causing the oil to boil. As a result, additives are destroyed and the lubricant darkens;
poor quality lubricant. This usually happens when it is bought in spontaneous markets or from suspicious sellers;
on the contrary, a high-quality lubricant is used, which quickly and thoroughly flushes a contaminated engine.

The fact is that during engine operation, the oil is constantly moving, while it collects carbon deposits, oxides, and other debris and brings it to the crankcase. Such a lubricating ability of the oil is due to the presence of various additives in it. Depending on the brand of lubricant used, the amount of additives in it will also be different, and each of them will play its role:

reduction of friction;
increase in viscosity;
temperature control and others.

One of the additives used in lubrication is alkaline. It allows you to remove chemicals that have entered the motor, reduces the likelihood of precipitation, removes carbon deposits and dirt. If there is little alkali in the oil used, the engine will wear out faster, a large amount of soot and various deposits will form faster.

Video: reasons for the rapid darkening of engine oil

What is the danger of darkened oil

Some drivers believe: if the lubricant has darkened, then it has used up its resource and it is necessary to replace it. However, not everything is so clear-cut here.

If for some reason you really used cheap low-quality oil, then when it gets dark, it is better to replace it. The use of such a lubricant will quickly clog the engine with dirt, soot and other deposits. As a result, its power will decrease and fuel consumption will increase. If you use such oil for a long time, then the motor can become very dirty and you will have to overhaul it, and this will entail serious costs of both time and money.

On the other hand, a quickly darkened high-quality oil may indicate a poor condition of the engine and its severe contamination. Therefore, first of all, it is necessary to rely not only on the color of the lubricant, but also on the engine resource, the age of the car, the frequency and quality of car care, driving conditions, and the quality of gasoline.

Preventive measures to prevent the rapid darkening of the oil

During engine operation, even the highest quality and most expensive oil will gradually darken. To avoid its rapid darkening and pollution, you must adhere to the following rules:

use only high-quality oil and buy it only in specialized stores and from trusted sellers;
for cars with high mileage, do not use low alkalinity grease;
monitor the condition of the engine and, if necessary, carry out repairs in time. It is motor malfunctions that most often cause rapid contamination of the lubricating fluid;
when changing the oil, flush the engine. Many owners ignore this step. You can perform this procedure both at the service station and on your own.

Engine flush features:

Some craftsmen flush the engine with kerosene or diesel fuel. Although they also help clean the motor, they have poor lubricating properties, unlike flushing fluid. Such amateur performance can lead to failure of the motor, so it's better not to risk it.

Video: how to flush the engine

Answering the question of whether black oil in the engine is “good” or, conversely, “evil”, we can say that this is rather good. Gradually darkening grease indicates that the motor is well flushed. But if it gets dark very quickly, then you should pay attention to the condition of the engine.

When using the machine, its parts gradually wear out. This cannot be avoided. Both spare parts and consumables that are poured into the car have a certain service life. In view of this, it is sometimes necessary to change the oil in the engine. All car manufacturers prescribe in the operating manual how often the lubricant needs to be changed. However, many drivers prefer to decide for themselves when a replacement is required.

The color of the oil matters. Some believe that if the oil has turned black, then you need to buy another one. Why does engine oil turn black? Does blackened car oil really indicate that it needs to be changed? Can I do it myself, or is it better to contact a car service?

Reasons why the lubricant darkens

Remember that when using any car oil will darken. This is due to various reasons. First of all, you need to deal with the car oil.

Today, the lubricant that is poured into the internal combustion engine on gasoline / diesel is a liquid consisting of many components that performs various tasks in the power unit, such as:

Formation of a lubricating film on contacting parts.
Heat sink. During the operation of the internal combustion engine, its parts rub, therefore, the temperature increases. If there is no heat sink, the metal will begin to become wider. Because of this, the engine may jam.
Washing of parts to eliminate contamination, the effects of wear. Due to friction, small chips of metal appear. It is abrasive, the motor wears out quickly.

The gases entering the crankcase from the cylinder block contain soot. Do not allow it to settle on the details.

Metal shavings and dirt after flushing remain on the crankcase bottom or in the oil filter. The lubricant dissolves soot with the help of special additives (alkalis).

Alkali neutralizes acids. If it is in the lubricant, foreign particles do not remain on the internal combustion engine parts. Due to the dissolution of soot and dirt in the car oil, it quickly darkens.

How fast does oil darken?

Many motorists are interested in how quickly the oil in the engine turns black. The color of the lubricant does not directly depend on the mileage of the car. The following factors are important:

oil quality;
additive substances included in its composition;
engine performance;
the level of deterioration and pollution.

If the engine is new, absolutely serviceable, then the color change of the lubricant depends on the elements included in its composition.

High-quality oil becomes darkened no earlier than after a couple of thousand kilometers. However, there are also many nuances here. The car oil may contain various additive substances. If a lubricant with a low concentration of alkali is poured into the motor, flushing will be carried out slowly, therefore, the oil will not darken quickly.

In any case, the grease will turn black. This does not always mean that it needs to be replaced. If the car oil remains light, think about it. Perhaps it does not flush the engine, which is why the parts are very dirty. In such a situation, it is advisable to replace the lubricant with another one.

Remember not to drive with more oil than the auto manufacturer recommends. This is due to the fact that when driving, the oil fluid consumes its own additive substances. In view of this, over time, she does not cope with her tasks (including washing).

Being deposited in the oil channels, dirt and soot will reduce their size and throughput. If you do not change the lubricant in time, the motor will be coked. The layer of dirt will become so thick that the new liquid simply cannot wash it off. This will affect the power of the engine, reduce its performance.

How engine malfunctions affect oil color change

Why does oil turn black quickly? One of the reasons for this phenomenon is the poor condition of the power unit. If the cylinder block and piston system are worn out, there is an increase in the volume of blown gases. Blackening oil becomes because of this.

Consequences of not timely oil change

If there is a problem with the power system in a gasoline engine, the lubricant will darken at an even faster rate. For example, due to incorrect adjustment, enriched fuel enters the cylinder block. Due to the high volume of fuel, this mixture will not be able to burn completely. Soot will appear, which will settle on the cylinder walls. Car oil, washing them, will remove soot, but it will remain in the lubricant, change its color.

In diesel engines, the oil liquid will darken much faster than in an internal combustion engine on gasoline (even if the unit is in full working order). This is due to the peculiarities of the fuel system and fuel.

When diesel burns, there is a lot of soot. It penetrates into the crankcase with burst gases. In view of this, in diesel ICEs, the lubricant darkens at a faster rate.

If you are worried about why the oil turns black, know that this is normal. No need to worry, because darkening is a good sign if it is gradual and does not interfere with the operation of the car.

It is much worse if the oily liquid does not change its own color. In the future, this will have a bad effect on the engine, because the dirt will clog the channels, therefore, oil starvation of the parts will begin. Because of this, the internal combustion engine jams.

For most drivers who have changed the brand of lubricant, the question arises why the oil in the engine turned black quickly. When a low-quality oil product is poured into the engine, a lot of dirt accumulates in it. After pouring high-quality grease, it washes away all contaminants. So that the next time the car oil does not change its color, reduce the replacement frequency by about half.

The oil filter also needs to be replaced occasionally. This will help reduce the amount of pollution. If the oil turns black quickly, the engine is probably worn out. Needs a complete overhaul.

Oil filter device

In order to understand why the grease quickly turned black, you need to check the engine for performance, measure the pressure under the hood. This will determine what the true cause of the darkening is.

How to proceed

When using a car, the best characteristic is a gradual change in the color of the oil. The main thing is the right choice of lubricant. Auto manufacturers prescribe in the operating manuals what are the indicators of the optimal car oil for the car. These guidelines must be followed. If the manufacturer recommends pouring synthetics / semi-synthetics, then you need to forget about the mineral water.

Consumables should be purchased only from trusted suppliers, choose products of popular brands. It costs more than lesser-known products, but it ensures the smooth functioning of the engine.

It is undesirable to switch to a different brand of motor oil, if there is no strong need for it. This should be done only when the lubricant does not perform its functions or is difficult to get.

Sometimes you need to flush the power unit. For this, special washers are used. Flushing must also be carried out when switching to another brand of oily liquid.

The washer is a conventional car oil, which contains many detergent components. Its use makes it possible to remove dirt from the crankcase before filling in new grease. Also, when flushing, the remains of the spent oil product remaining in the engine after draining are removed.

To clean the engine before filling, it is undesirable to use traditional methods, for example, diesel fuel. It could be used on old motors with a simple design. The use of a diesel engine in a modern internal combustion engine can lead to a major overhaul.

If, after washing the engine, the oil quickly darkens again, it is probably too clogged. To remove all the dirt, you will need to disassemble the engine, clean the oil channels with special cleaning agents.

Changing oil filters, regulating the operation of systems, and other types of maintenance not only guarantee the uninterrupted operation of the power unit, but also increase its service life, because the amount of combustion products polluting the internal combustion engine is reduced.

If the grease darkens too quickly, take action, because ignoring such a problem can lead to significant malfunctions.

darkening oil, then something is wrong, some car owners think. But is it really so? After all, it is one thing when it quickly turned black after replacement (still almost fresh), and another if after a couple of thousand kilometers.

There are several reasons why this happened - poor-quality lubricated fluid, dirty engine condition, long mileage of the car without replacement, switching to better oil, overheating, even due to poor fuel. How to understand when engine oil quickly darkens is good, and when is it bad? After all, this is not always a negative consequence and you need to worry. Then be sure to pay attention to additional factors and.

gradual aging and darkening is a natural process. Therefore, the main task of the motorist is to figure out whether the darkening is caused by positive or negative factors.

Dark oil is normal

So why does the oil in a car engine darken? Is it normal or not? The blackening process is due to the fact that, among other functions of the lubricating fluid, there is also a cleaning fluid. During the operation of the engine, fuel is burned with the appearance of complex chemical compounds, the composition of which largely depends on the type and quality of the fuel, but they are always harmful to the engine. These residues are located directly in the engine (on the cylinder walls, pistons, rings, and so on).

One of the tasks of the oil is to clean these deposits from the surface of the listed parts and maintain them in its composition, preventing them from being deposited in the engine. That is, the remains of fuel combustion pass into the composition of engine oil, and this leads to its natural darkening.

Dark oil in the automatic transmission appears for similar reasons - due to the cleaning of the box parts, in particular, due to the wear of the clutches. Moreover, ATF has high washing ability, and therefore quickly darkens. Plus, the degree of darkening depends on the mileage and the previously used lubricant.

Pay attention to the difference in fuel used and the degree of darkening of the engine oil in the engine. When diesel fuel is burned, darker exhaust gases are formed, and blacker deposits in the engine are similarly formed. This means that the oil darkens faster. As for engines running on gas (methane, propane, butane), the situation is reversed. Due to the chemical composition of the gas, there is less mud deposits (as in petroleum products), so they produce much cleaner exhaust gases. Accordingly, the engine oil in this case will be cleaner. And then, on the contrary, those who know that it should change its color will be interested in why the oil does not darken. With traditional use of gasoline, the condition of the engine oil will be somewhere in the middle between diesel and gas.

Oils designed for engine operation on gas do not darken so quickly, and there is a situation where the oil will not be very dark until it is changed.

Another important question in this context is after how many kilometers should the oil darken. If the oil darkens quickly (almost immediately after changing it or with a short run), this is an occasion to perform diagnostics and search for the causes, which will be discussed later. If the oil darkens naturally, approximately two to three thousand kilometers- this is most likely a natural darkening process, and if there are no additional symptoms of an engine malfunction (it works stably, not), then there is no reason to worry.

Reasons why the oil darkens

Using better quality oil

When there is a better quality oil in the crankcase than was used before, it will begin to darken faster, because it really began to clean, and not just lubricate. It is known that different manufacturers can differ in compositions not only, but also in the number of detergent additives (not to mention different types). Therefore, if a replacement was made, then there will be more washed out deposits in high-quality oil (which means it will be darker), than what it was before.

You can ride on such oil, but you need to carefully monitor its condition with a dipstick. If it looks uniformly viscous and uniformly dirty, then the cleaning process is going well. However, it makes sense to replace the lubricant a little earlier than it should be according to the regulations.

natural darkening

That is, the use of really high-quality oil. As described above, if the oil does not darken abruptly, but changes its color gradually, then everything is in order, and it simply does its job of cleaning the engine elements from carbon deposits and oxidation products, and at the same time keeps them in suspension (in a moving volume ).

Timely oil change provides reliable protection of engine elements from friction, overheating, excessive wear. And in the long run, it prevents the “oil burner”.

More or less high-quality oil becomes almost black (but not thick) by about 2 ... 3 thousand kilometers. If the oil is not of very high quality, then it will turn black somewhere around 800 ... 1000 kilometers, or vice versa, even after 3 thousand km it will remain light (when it does not have cleaning properties). This is true for gasoline engines. As for diesel engines, their oil turns black approximately twice as fast, that is, on some engines it can be dark even after a thousand kilometers.

Another interesting fact is that the engine oil will darken faster if the power unit has recently been overhauled. In this case, the darkening is caused by a large amount of metal chips formed as a result of the interaction of rubbing pairs. After the "capital", it is recommended to change the oil earlier than the deadline set by the regulations.

High ash content and low TBN

Engine oil is an indicator for determining additives that contain organic metal compounds (in particular, their constituent salts of zinc, potassium, magnesium, calcium, barium, sodium and other elements). In simple words, this indicator characterizes the number of fireproof elements during waste and the washing ability of the oil. Sulphated ash content in this context is interesting in that it is directly proportional to the base number (TBN).

Often in the performance characteristics of oils (on canisters or in the description in the store) you can find information about the value of sulfate ash content and / or base number. And so the higher they are- the higher the washing ability of the lubricating fluid, and hence the darker the oil will be during operation. And vice versa, the lower these values are, the more transparent it will be.

Therefore, the reason for the darkening of the oil can be a high ash content. But these values are selected and recommended by the automaker for a particular motor. Please note that oils with a low base number require more frequent replacement, approximately every 6-7 thousand kilometers. They are very sensitive to fuel quality and lose their properties faster.

Now let's move on to negative reasons, that is, those from which it is worth getting rid of.

Fake

The crankcase is filled with fake oil. Unfortunately, at present this problem is very relevant, because almost all popular brands of oils are clandestinely produced fakes. Naturally, their products are of very poor quality, do not fulfill the functions assigned to them, and, among other things, quickly darken. Such oil must be replaced with the original as soon as possible. Preferably flush the engine.

This also includes the case when the car owner buys low-quality oil of some little-known brand at a low or average price. Such compositions often have low performance characteristics, and as a result, they quickly lose them, which is expressed, among other things, in their rapid darkening.

Ingress of combustion products into the oil

In this case, the oil begins to quickly oxidize, loses its performance properties, and, among other things, changes its color to a darker one. The main reason here is depressurization, and it, in turn, can be caused by various reasons - breaking through the cylinder head gasket, damage to the oil scraper rings, and so on. Gasoline can also get into the oil, it dilutes it and changes its color. If there is a weakening of the oil scraper rings of the piston, then a situation arises when the oil, remaining on the walls of the cylinders, burns out along with the fuel. In this case, the oil will also turn black. As a rule, in this case, excessive consumption of lubricating fluid is observed.

In any case, you need to audit the engine yourself or seek help from a car service. If there is a malfunction of the engine, then within the framework of this article it is impossible to unequivocally answer the question of why the oil in the engine darkens.

Crankcase gases getting back into the engine

If the crankcase ventilation system is faulty, the latter can enter the engine again and come into contact with the lubricating fluid. Because of this, it oxidizes faster, loses its performance properties and darkens. And the more gases enter the engine, the faster the mentioned process occurs.

Poor quality fuel

Since the main cause of darkening of the oil is the combustion products of gasoline / diesel fuel, the composition of the fuel in this case is very important. The cleaner the fuel (made to a higher standard, does not have additional impurities), the darker the products of its combustion will be, and hence the darker the engine oil will be. Therefore, try to fill the tank with good fuel, this will not only increase engine power, but also protect it from excessive wear, and also increase engine oil life.

There is an opinion that in the CIS countries only diesel fuel has a lot of impurities, but in fact this is not so. Gasoline is also generally of poor quality. You can verify this by simply igniting it and looking at the color of the outgoing smoke.

Oil overheating

If the engine has been running for a long time or continuously under severe conditions (high ambient temperature, poor ventilation, high rpm/load), the engine temperature will naturally become very high. And as a result, the oil used too. Under such conditions, the lubricating fluid will literally “roast” and turn black. And this is all the more relevant, the older the oil is, firstly (a large mileage was made on it), and secondly, its level in the crankcase is lower.

In the worst cases, the lubricant can turn into a kind of fuel oil under difficult conditions, and this can lead to very sad consequences, up to an engine overhaul. Therefore, you should try not to operate the engine constantly under critical loads, or choose oils with appropriate performance characteristics (viscosity, tolerances, and so on). By the way, the wrong choice (very thick or, on the contrary, very liquid) can also often lead to overheating of the engine as a whole and the oil in particular.

Outcome

If the oil darkens gradually, and at the same time the engine is running normally, there is no reason to worry. Under normal conditions, the oil darkens after about two thousand kilometers. Then it starts to blacken and thicken. If the lubricating fluid acquired a dark shade very quickly (after a run of 300 ... 500, maybe up to a thousand kilometers for a gasoline engine, in some cases it can even immediately after replacement), then this is an occasion to think and perform engine diagnostics. If your car runs on gas, then the oil is usually transparent even with a significant mileage (however, you still need to change it according to the regulations, despite the transparency).

What to do if the engine oil darkens

The answer to the question "what to do?" depends on the cause of the darkening. We list general recommendations based on the above reasons and methods for preventing this phenomenon. That is, what actions to take so that the darkening is natural, and not “pathology”.

First. Buy original high-quality motor oil. associated with a large number of factors. Try to shop at trusted stores. There is currently a growing trend for popular lubricant manufacturers to protect their products online. That is, the authenticity of the oil canister can be checked using a smartphone connected to the Internet.

Second. Regularly monitor the condition of your vehicle's engine. Control the functioning of the elements of the cylinder-piston group, oil scraper rings, gaskets, seals, in a word, prevent mixing of fuel and oil in it.

Third. Regularly. Ideally, this should be done in accordance with the recommendations of the automaker. Usually, the corresponding value is indicated at 10 ... 15 thousand kilometers. However in this case it is better to judge by engine hours. Approximately after 250 ... 300 hours of engine operation, the additive responsible for the content of dark deposits in itself stops working, and deposits begin to settle inside. If, when checking the condition of the lubricant, it was found that it contains carbon deposits and / or solid particles, then it is better to replace it as soon as possible. In some cases, it makes sense to flush the engine with special compounds. As practice shows, when driving slowly in a metropolis (especially with numerous traffic jams), it makes sense to change the oil already at 7 ... 9 thousand kilometers.

Fourth. Constantly check the oil level in the engine crankcase with a dipstick, do not allow its value to fall below the MIN mark (but also harmful). Similarly, when the oil pressure warning light on the dashboard is activated, check its level without delay and top up the lubricant if necessary.

Fifth. Use the oil recommended by the car manufacturer. This applies to both viscosity values and other performance characteristics, in particular, automaker tolerances, API standards, ACEA, and so on.

sixth. When switching to a higher quality oil (with a large amount, including detergent additives), it makes sense to use an engine flush. However, this is not recommended if engine has high mileage and it constantly used not very high-quality oil. In this case, there is a risk that the detergent additives of the new lubricating fluid will remove coking from various places where friction parts are produced and / or microcracks in the oil system, and this will lead to its depressurization, oil leakage and compression loss.

High mileage engine can kill not only washing, but also use of oil with a large amount of detergent additives, especially if poor-quality lubricating fluid was previously filled in.

seventh. Change the oil filter in time. Its mandatory replacement is carried out when changing the oil. However, on many machines, regulations require that the corresponding filter be changed much more often. Read this information in the manual of your machine and follow the recommendations given there.

eighth. Try to fill the tank with good fuel, that is, refuel at proven gas stations, and vice versa, do not fill the car with any surrogate, which can often be found on sale at low prices.

ninth. Do not operate the engine at excessive loads and/or high speeds. If you need to use the machine at a high ambient temperature, you must ensure the normal operation of the engine ventilation system, as well as select an oil with the appropriate characteristics (viscosity and temperature tolerances).

tenth. Constantly monitor the good condition of the crankcase ventilation system. Do not allow them to get back into the engine. If you suspect a corresponding malfunction, you must immediately carry out an audit and, if necessary, repair.

Owners quite often note such a phenomenon when fresh engine oil quickly turns black after replacement. A burnt smell may also appear in the oil, which is clearly felt after 200-500 km. run. In a similar situation, many drivers are wondering if the engine oil should turn black and how quickly this happens.

At the very beginning, it should be noted that there may be several reasons for the blackening of the lubricant. In some cases, rapid darkening is normal, while in others it may indicate certain problems with the engine or the poor quality of the engine oil itself. In this article, we will look at the main reasons why oil quickly turns black, and also answer the question of why oil turns black in a gasoline or diesel engine.

Read in this article

Engine oil darkens

Let's start with the lubricant itself. It is well known that any motor oil is a mineral, synthetic or semi-synthetic base base, which also contains a package of active additives. These additives make it possible to comprehensively improve various performance characteristics of the lubricant: reduce friction losses, stabilize temperature indicators, extend the life of the oil and slow down its aging, provide a washing effect, etc.

In the list of chemical additives in the base base, a separate place is occupied by the indicator of the base number of a particular engine oil. In other words, alkali must be present in the lubricant. The main task of this additive is to neutralize acids that are formed in the internal combustion engine during the operation of the unit and then enter the lubrication system. Alkaline additives also actively fight the formation of deposits in the motor, wash off carbon deposits, coke, etc. Simply put, the alkali in the composition of engine oil protects against oxidation and performs detergent properties, allowing you to keep the power unit clean from the inside.

It turns out that the ability of the oil to wash off pollution will directly depend on the base number indicator. Given this feature, then the widespread assertion that high-quality car oil should practically not darken in the first 3-5 thousand kilometers after replacement is a profound delusion. Usually, drivers who dealt with similar products 15-20 years ago used to evaluate the quality of oil only by the rate of darkening. The fact is that in those years there were fewer additives and high-quality oil differed markedly from more affordable analogues in terms of pollution rate.

Simply put, the blackening of the oil was one of the main indicators for its replacement. Cheap lubricant could begin to darken after 400-800 km, while more expensive options remained clean for 2-3 thousand km, then gradually darkened to 5 thousand km. and then blackened. Note that the color of the lubricant did not change as a result of the action of additives, but taking into account the properties of the base oil. Today, the situation has changed dramatically, as modern motor oils contain a large number of active additives.

Darkening of the oil indicates that the lubricant retains and binds chemical components, deposits, etc. It turns out that acids do not have contact with parts, corrosion slows down and engine wear is minimized. During the process of changing the lubricant, contaminants merge with the used oil, and do not settle on the surfaces of the parts. In other words, everything turns out exactly the opposite - if the oil does not turn black for a long time, then it does not wash or clean the engine, and does not provide reliable protection against harmful products. The long transparency and purity of the oil indicates that the lubricant is simply not capable of performing cleaning functions.

It is also useful to know that if there are few alkaline additives in the composition of the lubricant, then if the service interval is exceeded, the engine will be subject to intense contamination and accumulation of deposits. In some cases, these contaminants lead to a decrease in the throughput of the channels of the lubrication system, as a result of which the pressure in the system decreases, the lubricant is supplied to the loaded friction pairs in insufficient volume, oil starvation and increased wear of the power unit occur.

In parallel with this, the temperature regime is violated at the interface points, an increase in the friction force leads to overheating. Also, clogging of the channels of the oil system does not allow the circulating lubricant to fully ensure heat dissipation. As a result, internal combustion engine parts are damaged, crankshaft connecting rod or main bearings turn, rockers fail, hydraulic compensators become clogged, etc. It is for effective counteraction and prevention of possible consequences that manufacturers add alkaline additives in a balanced way. We add that immediately after fresh lubricant enters the engine, the active work of the additive begins, that is, the lubricant ages. With mileage, the additive gradually loses its properties, the degree of protection of the engine from acids and deposits deteriorates, which is the reason for the next oil change.

It turns out that the service life of a modern lubricant is determined not by color, but by the indicator of how long the alkaline detergent additive will be in working condition. This feature is one of the main reasons why the lubricant must be changed taking into account strictly defined intervals (on average, 10-15 thousand km in the CIS, which depends on the quality of the fuel). It becomes clear that the oil is intended not only for lubrication, but also for cleaning. For this reason, its darkening during operation can be considered quite normal.

Note that the grease darkens especially quickly in motors that were initially contaminated. In other words, darkening means that the oil is actively washing the engine. Given this fact, the purity of the oil should be more alarming, that is, when its color practically does not change with mileage. This may indicate that the lubricant has low detergency and the engine is not being cleaned.

For a better understanding, it is enough to recall the features of the work. Engine oil is pumped from the engine crankcase using an oil pump, then circulates through separate channels. The lubricant protects the parts from dry friction, while carbon deposits and deposits are washed off, which then enter the crankcase. You also need to take into account the high temperatures at which the oil operates. As a result, the color of the material gradually changes to a darker one and this happens in a short period of time.

Engine oil turns black quickly

As already mentioned, the darkening of the oil indicates that it is working, that is, it actively cleans the engine of contaminants. It also happens that the oil does not just darken, but becomes black and more like fuel oil. In this case, this moment should be given special attention and find out why the oil in the engine turns black quickly.

At the very beginning, you need to remove the oil dipstick and wipe the oil from it with a clean rag. The remains of black stains will indicate that the lubricant in the engine is fading. The reason may be significant wear, that is, oil enters the combustion chamber. In parallel, the fuel also flows into the engine boat, diluting the lubricant. As a result, the working fluid of the ICE lubrication system loses its protective, detergent and other useful properties. It turns out that the rapid blackening of the oil indicates a problem with the engine itself. Additional symptoms are usually increased fuel and oil consumption, reduced engine power, difficult cold starting, etc.
The second reason that explains why the oil in a diesel engine quickly blackens or blackens the lubricant in a gasoline unit is overheating of the oil. A rapid color change to black occurs if the motor is constantly operated in heavy duty at high speeds and maximum loads. Also, the oil overheats when the lubricant was initially incorrectly selected according to the viscosity characteristics. In fact, boiling occurs, the lubricant becomes a homogeneous black mass.

It becomes clear that in case of problems with the CPG, the motor needs repair. If the oil is not suitable for this type of engine, then such a lubricant must be immediately replaced with a suitable option, which is recommended by the engine manufacturer and meets all tolerances. You should also not forget that a low-grade fake can be accidentally poured into the motor. For this reason, it is recommended to purchase fuel and lubricants only at trusted points of sale.

Remember, further operation of the engine with black oil can lead to serious damage to the power unit in the absence of existing problems, as well as additional problems when postponing repairs and lubrication changes on units in which oil blackening is noticed due to wear of individual elements.

How fast should engine oil turn dark or black?

So, all oils, regardless of types and brands, darken sooner or later. In this case, one product may blacken earlier or later than the other. Note that the darkening rate is influenced by a number of general and individual factors, among which experts distinguish:

the condition of a particular engine and the cleanliness of its lubrication system;
the amount of detergent additives in a particular lubricant;

It is quite obvious that if the lubrication system already has various deposits in the channels, then accelerated blackening can be considered normal. Moreover, the more detergent additives in a particular type of lubricant, the faster the lubricant will darken. It should also be borne in mind that after pouring fresh lubricant, it begins to actively wash off old deposits, which then accumulate not only in the oil itself, but also in. This means that during one service interval with rapidly darkening grease, it is better to change the filter twice or more. The replacement interval itself can also be reduced by 20-40%.

This approach will allow you to "softly" remove deposits that circulate through the oil system. In other words, the engine is gradually washed by the engine oil itself, which is changed prematurely, that is, before the start of the loss of cleaning properties. We add that for high-quality cleaning it may be necessary to carry out the procedure for replacing filters and oil according to this scheme not once, but several times.

Another cleaning method is the use of oil flushes, as well as a short operation of the internal combustion engine on the so-called flushing oils. Note that these methods have both advantages and disadvantages. In short, flushes have a negative effect on rubber seals, and can also lead to various unpredictable chemical reactions after mixing with the base lubricant.

An additional nuance is that after softening the deposits in the engine under the action of flushing, they can clog the channels of the lubrication system. In such cases, the risk of premature failure of the working power unit increases. If the oil began to quickly turn black due to the ingress of gases into the crankcase, then the motor needs to be replaced or.

In view of the foregoing, we can conclude that if the oil turns black, but the lubricant consumption remains normal, then you can start by cleaning the oil system. After removal of contaminants, the rate of blackening should return to normal or slow down noticeably. If there are problems in the mechanical part, then the problem will go away only after the repair of the power unit.

What is the result

As you can see, the rapid darkening of the oil today cannot be considered a sign of its poor quality. If the motor is in good condition, then the rate of change in the color of the lubricant to dark or black will depend on the degree of contamination of the engine and the base number of the oil used.

Under the same conditions, oils with fewer alkaline additives will darken more slowly and wash the engine worse than their highly alkaline counterparts. At the same time, a lubricant with high detergent properties can darken after 300-400 kilometers traveled. In parallel with this, the darkening of the oil does not mean that it is time to change it. Active additives and alkalis wash and then hold the dirt in the oil, allowing the lubricant to work throughout its declared service life.

We also add that when choosing a lubricant, a number of additional features should be taken into account, and not just its detergent properties. The fact is that oils with a high alkaline number have a short service life (on average, about 6-7 thousand km). The fact is that such products usually do not contain a large amount of additives that slow down the aging process of the lubricant. In other words, an oil with good detergency is designed for a shorter life and is subject to accelerated oxidation and aging, which means shorter intervals and more frequent changes.