It's not just engine parts that wear out
During the operation of a car, gradual wear of its components, especially the engine, occurs, and no matter how much we would like to prevent this, we cannot succeed. In this case, not only components and mechanisms are subject to wear, but also the working fluids poured into it.
Therefore, the list of engine maintenance work includes the replacement of technical fluids. It is especially important to change engine oil on time.
All automobile manufacturers indicate in their technical documentation what frequency should be between changing a given working fluid. But many motorists are accustomed to independently determining whether they can continue operating the engine with oil filled or whether it is time to replace it.
And they do this based on the color of the liquid - if the oil has become very dark, then it’s time to buy a new one and replace it.
Next, we will try to figure out whether the darkening of the oil is really a signal that it is time to go to the store for a new one, crawl under the car, or leave the replacement operation to specialists at a service station.
Why does engine oil turn black?
Let us immediately note that in any case, during operation, the oil will turn black, but this can happen for various reasons. First, let's look at the lubricant itself.
Modern oil for an internal combustion engine is a multicomponent liquid that must perform a number of important functions inside the engine.
The first is the creation of an oil film between surfaces to reduce friction between them. This film is formed during the process of lubrication of these surfaces.
The second function is to remove heat from the rubbing elements. While the engine is running, its components still rub, causing them to heat up. And if the heat is not removed, then due to excessive temperature the metal will begin to expand, which leads to jamming of the assembly.
And the third function is washing surfaces to remove wear products and dirt. All due to the same friction, small metal shavings are formed, which later act as an abrasive, increasing the wear of surfaces and the engine as a whole.
Dirt also acts in the same way. Gases escaping from the cylinders into the crankcase also carry polluting elements such as soot - and it is not desirable for them to settle on working surfaces.
And if metal shavings and dirt often settle to the bottom of the crankcase after flushing or are retained in the filter, then the oil dissolves the soot and retains it. For this purpose, it contains alkaline detergent additives.
Alkali is a universal solvent and acid neutralizer, and its presence in the lubricant prevents soot and other contaminants from settling on the surfaces of components. And since they do not settle anywhere, but linger in the oil, they will ultimately lead to a change in the color of the oil - its darkening.
Causes and consequences of blackening of engine oil - DRIVE2
Many owners of various brands of cars ask the same question at car services. They don’t understand why the motor oil running in their car engine darkens or turns black so quickly.
Someone immediately begins to make complaints about the fact that only low-quality lubricant turns black so quickly. Some people are not so categorical, but are worried about the condition of their engine, worrying that recently filled car oil turns black literally before their eyes, and the car owner can even smell a burning smell.
It is almost useless to argue on this issue, since the reasons for such darkening of the lubricating fluid can be very different. Car oil does not always turn black as a result of poor quality or engine malfunctions.
However, such situations occur quite often, so they are worth considering in more detail. Below we will try to understand why the oil darkens, as a result of which it darkens, and what the consequences and side effects may be.
About the speed and consequences of darkening Reasons why oil may turn black
It’s best to start from the very beginning - directly with car oil. Any modern lubricating fluid contains a large number of different additives. They are used to achieve various purposes during the operation of motor oil. They contain additives to reduce friction, additives that change the operating temperature properties of the oil, and many other auxiliary substances.
One of these lubricant additives is responsible for regulating the “base number” that the motor oil has. It turns out that the alkali it contains is a vital element. It neutralizes acids that penetrate into the oil system during operation, and also prevents the formation of deposits in the engine, removes varnish deposits, dirt and other debris.
Use additives in the motor. Additives improve the properties of the lubricant. When alkaline additives are contained in the motor oil in small quantities, the motor begins to wear out faster and become clogged with various deposits. An increase in the amount of such deposits leads to complications in the functioning of the engine for two main reasons:
In places of such contamination, the passage of oil becomes significantly more difficult, which leads to the so-called “oil starvation”.
There is a violation of the temperature regime of the engine, since deposits do not allow heat to escape. P
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How quickly should the grease turn black?
Many people wonder what color the oil should be at different mileage.
It is impossible to say unequivocally that with such and such a mileage its color should be this color, and with more mileage it should not change more, since this depends on several factors:
- lubricant quality;
- its additive package;
- technical serviceability of the power plant;
- the degree of wear and contamination.
Let's assume that the engine is new and technically fully functional, and the change in color depends entirely on the oil and its composition.
When using high-quality oil, its darkening will not occur earlier than after several thousand kilometers and this process will be gradual.
But here too there are many nuances.
Motor oil may contain different amounts of detergent alkaline additives.
So, in a lubricant with a low alkali content, the flushing process will be slow, and, therefore, the oil will turn black later.
Conversely, with a large amount of alkaline additives, the removal of pollutants will be more intense, and the material will darken earlier.
But in any case, the oil will darken and this is not a sign that it is time to change it, unless, of course, its service life has been exhausted. This is rather a signal that the material is of high quality and performs its functions.
But the lack of darkening after long-term use is not a good sign - the oil does not flush, and dirt settles on the surfaces. In this case, it is better to replace it with another type of working fluid.
It is worth noting that you should not use the lubricant for longer than that specified by the car manufacturer.
The fact is that the oil uses up its additives as it operates and eventually ceases to perform its functions, including flushing.
As a lubricant ages, it will be less able to remove contaminants from surfaces. These, in turn, will begin to affect heat transfer and friction.
By settling on the walls of the oil channels, dirt and soot will reduce their diameter and throughput. If you do not replace the lubricant in a timely manner, this will ultimately lead to coking - the contaminants on the surface will become so dense that the new lubricant simply will not be able to wash them off, and all this will affect the life of the power plant - major repairs will have to be carried out earlier.
Effect of motor malfunction on lubricant color change
We only looked at the oil, and found that the latter will darken as we work. The condition of the engine also affects the color change of the lubricant.
Wear of the cylinder-piston group will lead to a significant increase in the amount of gases escaping from the cylinders, which will cause a faster change in the color of the engine oil.
If the power system in a gasoline engine is misregulated, the darkening will occur even faster.
For example, due to incorrect adjustment, an enriched combustible mixture is supplied to the cylinders. Due to the large amount of fuel, this mixture will not be able to fully burn in the cylinders, which will result in the formation of soot that settles on the cylinder walls.
The oil, washing the walls, will wash away this soot and keep it in itself, while quickly darkening.
In diesel engines, the lubricant will change color much faster than in a gasoline engine, even if the engine is fully operational. The reason for this is the peculiarity of the fuel system and the fuel used in these engines.
Diesel fuel produces significantly more soot during combustion. Some of it will enter the crankcase along with the escaped gases. Because of this, the oil in diesel engines turns black faster.
As a short summary, we note the main reasons on which the rate of darkening of the oil depends:
- The amount of detergent additives in the composition of the lubricant (With a small amount of these additives, the darkening will occur gradually, since the alkali will not wash away contaminants intensively, but a large number of cleaning components in the lubricant will ensure faster washing and removal of dirt, but because of this the oil will be faster will darken);
- Cleanliness of the engine (A lot also depends on this. For example, the engine used low-quality oil, which did not wash away dirt well, and a large amount of it settled on the surfaces inside. Then the oil was replaced with a high-quality one, with a good additive package. Detergent components of the new lubricant will begin to actively remove dirt, causing the oil to quickly turn black);
- Technical serviceability of the engine and the degree of its wear (A serviceable and unworn engine will have a gradual darkening of the lubricant. A worn-out unit, in which the operation of the power supply, ignition or gas distribution system is disrupted, will very quickly cause a change in the color of the lubricant).
At the same time, we also found out that darkening of the oil is a natural process, and you shouldn’t be afraid of this, especially since this is a good indicator if the color change occurs gradually and you can continue to drive the car calmly.
It is much worse if the lubricant does not change its color; this can have a negative impact in the future, since dirt can clog the channels, leading to oil starvation of components and mechanisms. As a result, the engine may seize.
If the oil turns black after just a few tens of kilometers, then this is something to think about. This can happen after changing the brand of lubricant.
For example, at first a low-quality fluid was used, which is why large amounts of pollutants accumulated inside the engine. After filling in a good lubricant, it began to actively wash away the dirt.
In this case, you can do differently - use an engine flush or continue to use the filled oil, but significantly reducing the mileage until the next replacement, for example, not 10 thousand km, but 5 thousand.
In this case, it is advisable to periodically change the oil filter. This will slightly reduce the amount of dirt in the oil.
The second option in case of rapid darkening is severe wear of the engine and the need for major repairs or improper operation of its systems.
To understand the reason for the rapid blackening of the lubricant, first of all, it is necessary to check the performance of the engine systems, and also measure the compression, which will make it possible to understand why the lubricant quickly changes color - from malfunction and wear of the engine, or from the oil itself.
Why does the oil in a diesel engine turn black?
Very often, owners of cars with diesel engines express their concerns about the dark color of the oil in the unit. They changed the oil just the other day, and it was already black.
As you know, the internal combustion engine is the most important element in the vehicle system, and its breakdown can lead to significant and unplanned expenses. Therefore, concerns of this kind are not entirely groundless. With the help of the service center specialists Autocentre GAZ Tolyatti - official GAZ dealer, we will try to figure out what’s wrong.
With the transition of technical stations to semi-synthetic and synthetic oils, such questions are not uncommon among customers. I would like to note right away that the oil in diesel internal combustion engines operates under more severe conditions than in its gasoline counterparts. This is due to the high pressure on the oil film in the plain bearings due to the high compression ratio. In addition to lubricating functions, diesel oil has the function of cooling the connecting rod and piston group, so the oil volume is always greater than in gasoline engines, and some diesel cars are equipped with a special oil cooler.
During operation of a diesel engine, due to the presence of sulfur in the fuel, a sufficient amount of soot is formed, which, together with a small amount of exhaust gases, enters the crankcase. Diesel fuel at domestic gas stations has a sulfur concentration that is several times higher than in Europe. This is one of the factors affecting the color of diesel oil.
Modern semi-synthetic and synthetic oils have high cleaning characteristics. As a result, the internal cavities of the engine remain clean until a certain resource point, associated with the ability of the oil to actively absorb soot, especially during the first kilometers after replacement. Therefore, when a client, literally the next day, checking the oil level after changing it, finds black oil on the dipstick, he may be perplexed about this.
Thus, it becomes clear that if, as a result of replacement, the oil remains light, the conclusion is clear - the oil does not wash and all the soot remains on the inner walls of the internal combustion engine.
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