Many car owners do not know how often to change the oil in their car’s engine or doubt the data provided by the manufacturer on the frequency of replacing consumables. And for good reason. Replace via every 10-15 thousand kilometers often not entirely true.
It is better to be guided by the number of engine hours worked and the average speed . There are many components to the answer to the question of how often to change engine oil. Among them are the recommendations of the car manufacturer, operating conditions of the car (heavy/light, in the city/on the highway, often/rarely used), mileage before changing the oil and total mileage, technical condition of the car and the oil used.
Also, the frequency of engine oil changes is influenced by additional factors - the number of engine hours, engine power and displacement, time since the last oil change (even without taking into account the operation of the machine). Next, we will tell you in detail about how often to change the engine oil, what it is like, and other things that will probably be useful to you.
For those who do not want to go into details and understand everything in detail, we will immediately give an answer regarding the change interval: in urban conditions, the oil “works” for 8-12 thousand, on the highway/light driving mode without traffic jams it lasts up to 15 thousand km. The most accurate way to find out when to change it can only be obtained from a laboratory analysis of the oil used.
What affects the replacement frequency
Each car manufacturer provides detailed information in the car manual about when to change the engine oil. However, the fact is that this information is not always correct. As a rule, the documentation contains a value of 10...15 thousand kilometers (in each individual case the number may differ). But in reality, several factors influence the mileage between replacements.
10 indicators that affect the timing of engine oil changes
- Type of fuel (gas, gasoline, diesel) and its quality
- Engine capacity
- Brand of previously filled oil (synthetic, Semy-Synt, mineral oil)
- Classification and type of oils used (API and longlife system)
- Engine oil condition
- Replacement method
- Total engine mileage
- Technical condition of the car
- Operating conditions and modes
- Quality of consumables
The manufacturer's instructions are not included in this list, since for him the service interval is a marketing concept.
Operating modes
First of all, the timing of engine oil changes is affected by the operation of the vehicle . Without delving into the essence of the various transient processes, it is worth mentioning two main modes - on the highway and in the city. The fact is that when a car drives along the highway, firstly, the mileage accumulates much faster, and secondly, normal cooling of the engine occurs. Accordingly, the load on the engine and the oil used in it is not so high. On the contrary, if the car is used in the city, then its mileage will be significantly lower, and the load on the engine will be higher due to the fact that it often stops at traffic lights and traffic jams with the engine running. The cooling will be insufficient.
In this regard, it would be more intelligent to calculate how long it takes to change the engine oil, based on engine hours , as is done in truck, agricultural and water equipment. Let's give an example. The car will travel 10 thousand kilometers in urban conditions (at an average speed of 20...25 km/h) in 400...500 hours. And the same 10 thousand on the highway at a speed of 100 km/h - in only 100 engine hours. Moreover, the operating conditions of the engine and oil on the highway are much milder.
Driving in a metropolitan area is rightly equated to driving on rough off-road conditions in terms of how it destroys oil. This is especially true when its level in the crankcase is below average, and even worse when it is less than the minimum level. Also remember that in hot summer weather the oil is subject to a much greater load due to high temperatures, including from the hot surface of roads in big cities.
Engine size and type
What affects the frequency of oil changes
The more powerful the engine, the easier it is for it to survive load changes, as well as difficult operating conditions. Accordingly, the oil will not have such a strong impact. For a powerful engine, driving along the highway at a speed of 100...130 km/h does not place a significant load; it will be below average. As the speed increases, the load on the engine, and therefore on the oil, will change smoothly.
Small cars are another matter. As a rule, they are equipped with a “short” transmission, that is, the gears are designed for a small speed range and operating speed range. Accordingly, small engines experience greater loads in critical conditions than powerful ones. When the load on the engine increases, the temperature of its pistons also increases, and the amount of crankcase gases also increases. This leads to a general increase in temperature, including oil temperature.
It’s especially hard for small-displacement forced engines (for example, 1.2 TSI and others). In this case, the load is also supplemented by a turbine.
Additional factors
This includes high temperature control (operating temperature), poor ventilation of the engine crankcase (especially when driving in urban conditions), the use of low-quality or unsuitable oil for a given engine, the presence of dirt in the oil channels, a clogged oil filter, and the operating temperature range of the oil.
It is believed that the optimal engine oil change interval is from 200 to 400 operating hours under various operating conditions, with the exception of maximum load, including driving at maximum speed and maximum rpm.
The type of oil used is also of great importance - mineral, semi-synthetic or fully synthetic. You can read about each of the mentioned types separately using the links provided.
Fuel quality
Fuel affects the frequency of oil changes, primarily due to the possibility of sand, dirt or water being introduced into it. All this almost always happens at unverified gas stations.
- Oil, in addition to chips and scale from natural use, also absorbs excess dirt, which in theory should not have been there.
- This significantly reduces its service life and accelerates aging. And frequent oil changes can neutralize all the negative effects of low-quality fuel.
Why do you need regular oil changes?
Indication on the dashboard
What can happen to a car if you don’t change the engine oil for a long time? To answer this question, you need to understand what functions it performs. Any oil consists of a so-called “base” and a certain amount of additives. They are the ones who protect engine parts.
During the operation of the machine, and even its parking, continuous chemical destruction of additives occurs. Naturally, this process is faster when driving. In this case, natural deposits form on the engine crankcase, oxidation processes occur with individual components of the oil, its viscosity and even the pH acidity level change. These facts are the answers to the question - why change the oil once a year at least .
Some automakers and motor oil manufacturers indicate how long it takes to change the engine oil not by mileage, but by frequency, usually by month.
And under significant load, the described processes in the oil occur at an even greater speed. Especially at high temperatures. However, modern manufacturers are constantly improving the technologies and chemical compositions of their oils. Therefore, they are able to withstand pollution and high temperatures for a long time.
In many modern cars, the ECU constantly monitors when to change the engine oil. Naturally, this decision is made on the basis of empirical methodology. It is based on actual data - average engine speed, oil and engine temperature, number of cold starts, speed limit, and so on. In addition, the program takes into account errors and technical tolerances. Therefore, the computer only reports an approximate time when the engine oil needs to be changed.
Unfortunately, on store shelves not only in the Russian Federation, but also in other CIS countries, a large number of low-quality or simply counterfeit motor oils are currently sold. And given that our fuel is often of poor quality, the frequency of oil changes still needs to be adjusted. In particular, if we talk about how many kilometers to change the engine oil, then the recommended amount should be reduced by about a third. That is, instead of the often recommended 10 thousand, change it after 7...7.5 thousand.
Change the oil AT LEAST once a year, regardless of whether you drive the car or not. In any case, the shelf life of engine oil is from six months to 1 year maximum.
We list the causes and consequences of untimely replacement of engine oil:
Engine deposits
- Formation of sediments . The reasons for this phenomenon lie in the process of destruction of additives or contamination of the oil with combustion products in the engine crankcase. The consequences are a significant decrease in engine power, an increase in the content of toxic substances in the exhaust gases, and their blackening.
- Significant engine wear . Reasons: oils lose their properties due to changes in the composition of additives.
- Increasing oil viscosity . This can happen for the same reasons. In particular, due to oxidation or disruption of polymerization of additives due to improper selection of oil. Problems arising from this include difficulties with oil circulation, significant wear of the engine and its individual elements. And the resulting oil starvation of the engine can lead to difficulties starting when cold; in critical cases, even engine failure is possible.
- Rotating the connecting rod bearings . This occurs due to the oil channel becoming clogged with a thickened compound. The smaller its cross-sectional area, the greater the loads the connecting rod bearings are subjected to. Because of this, they overheat and turn over.
- Significant wear of the turbocharger (if equipped). In particular. there is a high risk of damage to the rotor. It occurs because waste oil has a significant impact on the compressor shaft and bearings. As a result, they develop damage and scratches. In addition, dirty oil leads to clogging of the compressor lubrication channels, which can lead to it jamming.
Do not operate the machine with burnt and thickened oil. This exposes the motor to significant wear.
The problems described above are typical for vehicles operating in urban environments. After all, it is considered one of the most difficult for the engine. Below we present interesting factual data that were obtained experimentally. They will help you decide at what mileage to change the engine oil.
Advice from experienced drivers
Experienced drivers give some good advice about changing car oil:
- If the car is manufactured for more than seven years, then the oil should be changed 20-30% more often than in previous years.
- If you buy a used car, it is best to change the fuel oil first.
- You should not abuse express car oil changes; there is no better way than a complete replacement.
- When adding fresh oil, be sure to install a new filter.
- Under no circumstances should previously used fuel oil be poured into the engine.
- For a diesel car, it is better to use oil of the same brand and model.
- For unforeseen situations, there should always be 1 liter of fuel oil in the trunk of the car.
Even if the car has been sitting in a garage for a year, you should still change the oil, since it is a chemical product and it still loses its properties over time.
Results of experiments with oils
Specialists from the famous automobile magazine “Behind the Wheel” conducted six-month studies of several types of synthetic oils under operating conditions in city traffic jams (at idle speed). To do this, the engines operated for 120 hours (the equivalent of 10 thousand kilometers on the highway) at 800 rpm without cooling. As a result, interesting facts were obtained...
First, the viscosity of all motor oils during prolonged idling up to a certain (critical) moment is significantly less than when driving “on the highway”. This occurs due to the fact that at idle speed, exhaust gases and unburnt fuel leak into the engine crankcase, where it is all mixed with oil. In this case, there may be some (insignificant) amounts of oil in the fuel.
The drop in viscosity of motor oil is about 0.4...0.6 cSt (centistokes). This value is within 5...6% of the average level. That is, the viscosity is within normal limits. However, this only happens up to a certain point.
Clean and used motor oils
At approximately 70...100 engine hours (each oil is different, but the trend is the same for all), the viscosity begins to increase sharply. And much faster than when working in the “track” mode. The reasons for this are as follows. The oil is constantly in contact with the products of incomplete combustion (as discussed above), and reaches its critical saturation. The mentioned products have a certain acidity, which is transferred to the oil. Also affected is the lack of ventilation and low turbulence of the air-fuel mixture due to the fact that the piston moves relatively slowly. Because of this, the rate of fuel combustion is lower than average, and the entry of exhaust gases into the crankcase is maximum.
The widespread belief that a large amount of dirt forms in the engine when idling has not been experimentally confirmed. However, the amount of high-temperature deposits was small, and the amount of low-temperature deposits was large.
As for wear products, their amount is significantly greater in oil used in the “plug” mode than in the one that was used on the “highway”. The reason for this is the low speed of the pistons, as well as the high operating temperature of the oil (lack of ventilation). As for waste, each oil behaves differently. However, it can be argued that due to high operating temperatures and increased density, waste will also increase.
Based on the information provided, we will try to systematize the data and answer the question of how many kilometers to change the engine oil.
Recommendations for changing engine oil
Next, we will dwell in more detail on the question of how often to change the engine oil. As stated above, car manufacturers' recommendations should be taken with a grain of salt. Don't completely ignore them, but make your own amendments . If you drive your car only in city conditions (statistically, this is the majority of car owners), this means that the oil is used under heavy duty conditions. Remember that the less oil in the crankcase, the faster it ages. Therefore, its optimal level is slightly below the maximum mark on the indicator dipstick.
After how many thousand do you change the engine oil?
Calculation of engine hours for oil changes
We wrote above that it is better to calculate the frequency of oil changes based on engine hours. However, the complexity of this technique lies in the fact that sometimes it is difficult to convert kilometers into engine hours and get an answer based on this information. Let's take a closer look at two methods that allow us to empirically , but quite accurately, calculate how often to change synthetic (and not only) engine oil. To do this, your car must have an ECU that shows the average speed and fuel consumption over the last at least one thousand kilometers (the longer the mileage, the more accurate the calculations will be).
So, method one (calculation by speed). To do this, you need to know the average speed of your car over the last few thousand kilometers and the car manufacturer's recommendations at what mileage you need to change the oil. For example, the mileage before an oil change is 15 thousand kilometers, and the average speed in the city is 29.5 km/h.
Accordingly, to calculate the number of engine hours, you need to divide the distance by the speed. In our case it will be 15000 / 29.5 = 508 engine hours. That is, it turns out that in order to change the oil under these conditions, it is necessary to use a composition with a service life of 508 engine hours. However, in reality, such oils simply do not exist today.
We offer you a table showing the types of motor oils and their corresponding engine hour values according to API (American Petroleum Institute):
| Table of correspondence between oils and service life hours | |
| Oil type | Resource number of engine hours |
| Mineral | 150 |
| Semi-synthetic | 250 |
| Synthetic oils | |
| API SJ/SL | 250 |
| API SM/SN | 300…350 |
| Polyalphaolefins | 350…400 |
| Esthers | 400…450 |
Let's assume that the car engine is filled with SM/SN class oil, which has a working life of 350 hours. To calculate the mileage, you need to multiply 350 engine hours by the average speed of 29.5 km/h. As a result, we get 10325 km. As you can see, this mileage is very different from what the automaker offers us. And if the average speed is 21.5 km/h (which is more typical for large cities, taking into account traffic jams and downtime), then with the same 350 engine hours we will get 7525 km of mileage! Now it becomes clearly clear why it is necessary to divide the mileage recommended by the car manufacturer by 1.5...2 times .
Another calculation method is based on the amount of fuel consumed. As initial data, you need to know how much fuel your car consumes per 100 km according to its passport, as well as this actual value. It can be taken from the same ECU. Let’s assume that according to the passport the car “takes” 8 l/100 km, but in fact – 10.6 l/100 km. The mileage for replacement remains the same - 15,000 km. Let's derive the proportion and find out how much theoretically spend to cover 15,000 km: 15,000 km * 8 liters / 100 km = 1200 liters. Now let's make similar calculations for actual data: 15000 * 10.6 / 100 = 1590 liters.
Now we need to calculate at what distance the actual oil change (that is, how long the car will travel on a theoretical 1200 liters of fuel). Let's use a similar proportion: 1200 liters * 15000 km / 1590 liters = 11320 km.
We present for you an electronic calculator that will allow you to calculate the actual mileage before an oil change using the following data: theoretical fuel consumption per 100 km, actual fuel consumption per 100 km, theoretical distance to an oil change in kilometers:
However, the simplest and most effective method of checking is a visual inspection of the condition of the oil. To do this, do not be lazy to periodically open the hood and check whether the oil has thickened or burned. Its condition can be assessed visually. If you see that oil is dripping from the dipstick like water, then this is a sure sign that the oil needs to be changed. Another interesting method of checking is by spreading the composition over a napkin. Very thin oil will form a large and runny stain, which will tell you that it is time to change the fluid. If this is the case, immediately go to a car service center or carry out the procedure yourself.
How often to change the oil in a diesel engine
As for diesel engines, the same calculation logic applies here as for gasoline units. It is only necessary to take into account that the working fluid in them is exposed to greater external influences. As a result, diesel oil needs to be changed a little more often. In addition, domestic diesel fuel has a high sulfur content, which has a detrimental effect on the car engine.
Regarding the readings given by the car manufacturer (this is especially true for Western manufacturers), they, similar to gasoline engines, must be divided by 1.5...2 times. This applies to cars, as well as vans and small trucks.
As a rule, most domestic car owners of cars with diesel engines change the oil every 7...10 thousand kilometers, depending on the car and the oil used.
In theory, oil selection is based on the total base number (TBN). It measures the amount of active anti-corrosion additives in the oil and indicates the tendency of their compositions to form deposits. The higher the number, the greater the oil’s ability to neutralize acidic and aggressive products formed during oxidation. For diesel engines, TBN is in the range of 11...14 units.
The second important number characterizing the oil is the total acid number (TAN). It characterizes the presence of products in the oil that provoke an increase in corrosion and wear rate of various friction pairs in a car engine.
However, before deciding how many engine hours to change the oil in an engine running on diesel fuel, you need to understand one nuance. In particular, is it possible to use motor oils with a low base number (TBN) in countries with low-quality fuel (in particular, Russian, which contains a large amount of sulfur)? During the operation of the engine, and, accordingly, the oil, the alkaline number drops, and the acid number increases. Therefore it is logical to assume. that the intersection of their graphs at a certain mileage of the car tells us that the oil has completely exhausted its service life, and its further use only destroys the engine. We present to your attention test graphs for four types of oils with different acid and base numbers. For the experiment, four types of oils were taken with conventional names of letters of the English alphabet:
- oil A - 5W30 (TBN 6.5);
- oil B - 5W30 (TBN 9.3);
- oil C - 10W30 (TBN 12);
- oil D - 5W30 (TBN 9.2).
As can be seen from the graph, the test results were as follows:
- oil A - 5W30 (TBN 6.5) - was completely used up after 7000 km;
- oil B - 5W30 (TBN 9.3) - was completely used up after 11,500 km;
- oil C - 10W30 (TBN 12) - was completely used up after 18,000 km;
- oil D - 5W30 (TBN 9.2) - was completely used up after 11,500 km.
That is, the oil for heavily loaded diesel engines turned out to be the most durable. What conclusions can be drawn based on the information provided:
- A high base number (TBN) is critical for those regions where diesel fuel of poor quality (in particular, with high S impurities) is sold. Using this oil will provide you with longer and safer engine operation.
- If you are confident in the quality of the fuel you use, then it will be enough for you to use oils with a TBN value in the region of 11...12.
- Similar reasoning is valid for gasoline engines. It is better to fill in oils with TBN = 8...10. This will give you the opportunity to change the oil less often. If you use oil with TBN = 6...7, then in this case be prepared to change the fluid more often.
For general reasons, it is worth adding that diesel engines need to change oil a little more often than gasoline engines. And it is worth choosing it based on the value of the total acid and alkaline numbers.
conclusions
Thus, each car owner must decide for himself how often to change the engine oil. This must be done taking into account individual circumstances. We recommend that you use the calculation methods for engine hours and gasoline consumption given above (including calculators). In addition, always visually assess the condition of the oil in the engine crankcase. This way you will significantly reduce the wear and tear on your car’s engine, which will save you from the need to carry out expensive repairs. Also, when replacing, buy high-quality oils recommended by the manufacturer.
Conclusion
Thus, it is necessary to determine the timing of oil changes taking into account individual circumstances. It is recommended to use the methods for calculating engine hours and gasoline consumption described above, as well as visually assess the condition of the lubricant in the engine crankcase.
Timely oil changes will significantly reduce wear on the power unit and eliminate the need for expensive repairs.
Regardless of the operating conditions of the vehicle, new lubricant should be added at least once a year - even if the vehicle has not been used all this time. In urban conditions, the oil “works” for 8-12 thousand kilometers, on the highway or in easy mode – up to 15 thousand kilometers.
You should not constantly use the express oil change service. During a rapid vacuum operation, a fairly large amount of waste lubricant remains in the engine oil lines. After adding fresh fluid, a “cocktail” of dubious quality is formed in the crankcase. That is why the replacement should be carried out in detail; it is even better to trust it to professionals in the car service.
