There are many reasons why an engine can “take” oil; sometimes it is very difficult, and sometimes even impossible, to find out why an engine “eats” oil at home. Today I will try to talk about the most likely reasons why a motor may increase engine oil consumption.
Let's dot all the i's right away. What does it mean the engine is burning oil or the engine is taking oil? Some literally understand this driver's expression, imagining an engine that is powered by motor oil. 🙂 This, of course, is nonsense, the expressions take or eat mean excessive consumption of engine oil, which should not exist. That is, the manufacturer indicated that the engine will consume 1 liter of engine oil per 10,000, this is considered the norm and there is no reason to worry. For example, when you have changed the oil, fill the engine with, say, 5 liters, you must be prepared for the fact that after 10,000 km you will have to add oil to the engine of your car. If you have to top up more often or more, this is called - the engine is consuming oil.
Where does this oil go?
As you know, all rubbing elements are lubricated with oil, without this it is impossible to imagine any internal combustion engine. The permissible oil consumption, as a rule, arises from the piston group of the engine, in this place the friction is greatest. Due to high temperatures, part of the engine oil burns out, “flying out into the pipe” along with the exhaust or depositing on the walls of the combustion chamber, piston rings or valve seats.
Note: You should not take the figure I gave above, 10,000 km and 1 liter of oil, as a rule; for each car this figure can differ significantly, it all depends on the brand of the engine and its features.
Increased fuel consumption indicates engine malfunctions; very often the cause is engine wear. As a rule, it all starts with oil appearing in the ventilation system; gradually, if nothing is done, oil will appear in the air filter. The reason for this is the pressure of crankcase gases, which increases as the engine wears, and oil is pushed into the breather.
Turbocharged engines can burn oil very quickly, drying out the engine sump due to simple wear and tear on the turbine rotor bushings. That is why owners of such engines should be extremely careful and promptly monitor oil consumption, starting with the turbine.
Reasons why the engine consumes oil?
Valve seals very often cause increased engine oil consumption. Oil seals are installed on the valves of the gas distribution system. Unexpected phenomena are possible here. For example, a poorly warmed-up engine increases the likelihood of hardening of the cap seals significantly, and there is no need to talk about used engines. A “hardened” cap will not provide a seal, therefore, oil will flow freely under the guide sleeve, along the valve stem. After this, the engine oil will either fly out along with the exhaust gases, or enter the combustion chamber and, burning, cover the spark plugs. The result is and.
Piston rings are the second most likely reason why an engine is burning oil. One piston usually has three rings, two compression rings on top, and one oil scraper ring underneath them. I hope you know what compression rings are for. With their help, the manufacturer reduces the gap between the piston and the cylinder wall, resulting in maximum efficiency of the transmitted energy for engine rotation. In order to reduce the friction that occurs between the compression rings and the cylinder walls, oil is supplied to them, the remains of which are removed by the oil scraper rings. Wear of these rings leads to the fact that some of the oil will remain on the walls, therefore, oil consumption will increase. As a result, one day you will miss several liters of engine oil and come to the conclusion that the engine is eating oil.
During its “life”, the motor undergoes a large number of heating and cooling cycles. At the same time, all engine parts are tested. Wear of piston rings or loss of elasticity, in addition to piston rings, is also fraught with the occurrence of a phenomenon called flutter. This phenomenon has been little studied, but one thing is known for sure: when the engine is running, the ring can oscillate along the piston radius with a high frequency, or can repeatedly jump from one edge of the piston groove to the other. Due to such fluctuations, the engine consumes almost liters of oil; most often this malfunction manifests itself in the form of characteristic blue smoke from the exhaust.
Low quality motor oil, as well as oil that does not match the type of engine, also often causes the engine to start to take oil. This reason indirectly affects the previous malfunction. The fact is that each engine has its own oil; if it is chosen incorrectly, its consumption can increase significantly. Due to the fact that the oil is too liquid, the piston rings cannot “collect” it and it remains on the cylinder walls and, after the fuel-air mixture is ignited, it burns along with it. As a result, it either “flies out” with the exhaust, or is deposited in the combustion chamber or on spark plugs, but no matter how you look at it, the oil level will constantly decrease. Also, often the “wrong” oil is deposited in a thick oily layer on engine parts, this can lead to “slipping” or. If the rings are stuck, compression is lost in all engine cylinders.
There are other reasons why an engine takes oil, such as natural wear and tear. In this case, a comprehensive production of all engine parts occurs. As a result, oil is lost many times faster than during normal operation. Engine wear most often involves deformation of the cylinder walls as the engine continues to be used. An increased gap between rubbing surfaces, cracks and chips and scuffs on the cylinder walls, as well as burnt-out cylinder head gaskets lead to oil leakage and a drop in its level. Residues of oil burn out or are deposited on parts; it is quite difficult to predict what the consumption will be in this case, it all depends on the degree of wear and damage to the internal combustion engine.
In conclusion I would like to add...
You should also be aware of replacement cycles. Remember that timely replacement will save you from many problems, including such an unpleasant phenomenon as excessive consumption of engine oil. Also, do not forget to promptly use special flushing oils. Buy only high-quality motor oil from a trusted manufacturer, the one recommended by your dealer or the one specified in the owner’s manual for your car.
Others do it yourself.
The problem of increased oil consumption very often worries owners of those cars whose mileage is already quite high after purchase or major repairs. But even on new cars, the engine often begins to consume oil beyond measure. To understand the reason for this, first let's look at a little theory on the matter.
For domestically produced cars, such as the VAZ 2106-07, or later models 2109-2110, the permissible oil consumption during engine operation is 500 ml per 1000 km. Of course, this is the maximum, but still, such consumption is clearly not worth considering as normal. In a good, serviceable engine, from replacement to oil change, many owners do not add a single gram. This is an excellent indicator.
The main reasons why an internal combustion engine consumes oil excessively
So, below is a list of reasons why a car engine begins to eat oil too quickly and in large quantities. I would like to immediately note that this list is not complete and is made on the basis of the personal experience of many experienced owners and specialists.
- Increased wear of the piston group: compression and oil rings, as well as the cylinders themselves. The gap between the parts becomes larger, and therefore oil begins to enter the combustion chamber in relatively small quantities, after which it burns along with gasoline. With such symptoms, you can usually notice either heavy oil deposits or a black coating on the exhaust pipe. A major overhaul of the engine, replacement of piston group parts and boring of cylinders if necessary will help eliminate this problem.
- The second case, which is also quite common, is wear of the valve stem seals. These caps fit onto the valve from the top side of the cylinder head and prevent oil from entering the combustion chamber. If the caps become leaky, the consumption will correspondingly increase and the only solution to this problem will be to replace the valve stem seals.
- There are times when everything seems to be fine with the engine, and the caps have been changed, but the oil continues to fly away into the pipe. Then you should pay special attention to the valve guides. Ideally, the valve should not dangle in the bushing and the gap should be minimal. If the play is felt by hand, and especially strong, then it is necessary to urgently change these same bushings. They are pressed into the cylinder head and it is not always possible to do this at home, although most succeed.
- Oil leakage through oil seals and gaskets in the engine. If you are sure that everything is fine with the engine, and cannot understand why the oil is leaking, you should pay attention to all the gaskets, especially the pan. And also check the seals to see if they are leaking. If damage is found, the parts must be replaced with new ones.
- It is also worth keeping in mind that your driving style directly affects how and how much oil your engine will consume. If you are used to a quiet ride, then you should not have any problems with this. But if, on the contrary, you squeeze everything out of your car that it is capable of, constantly operate it at high speeds, then you should not be surprised at the increased oil consumption.
These were the main points that are worth considering if you suspect that your internal combustion engine's appetite for fuel and lubricants has increased. If you had a different experience, you can leave your comments below on the article.
The problem of engine oil consumption worries many car enthusiasts. As you know, lubricant consumption is one of the important indicators of the overall condition of the engine. You can hear from some car owners that the engine does not take oil, that is, the level remains the same or remains within acceptable limits from replacement to replacement.
Others note increased or high oil consumption in the engine, which causes the need. Let us immediately note that the manufacturers themselves separately indicate the oil consumption rates in the engine. This means that the power unit can consume lubricant within certain limits, and such consumption is not a malfunction.
This phenomenon is usually called oil consumption due to waste. However, exceeding the norm for adding oil to the engine may well indicate problems with the internal combustion engine, engine, etc.
In this article we will look at what kind of “oil appetite” of various power units can be considered acceptable, as well as what factors and features affect lubricant consumption in internal combustion engines.
So, let's start with the fact that all engines consume motor oil to a greater or lesser extent. This happens taking into account the design features of the internal combustion engine, namely due to the urgent need to lubricate components and parts. In other words, the main loss of lubricant occurs as a result of the need to supply lubricant to the cylinder walls.
This area in the engine is a heat-loaded area. For this reason, partial evaporation and combustion of the lubricant occurs. Also, some of the oil is not removed from the cylinder walls, as a result of which the remaining lubricant burns along with the fuel in the combustion chamber.
As a rule, in modern engines the declared oil consumption is, on average, from 0.1 to 0.3% of the total fuel consumption that was expended to overcome any part of the journey. It turns out that if the car has traveled 100 km, and the consumption is 10 liters of fuel, then the norm will also be to consume, on average, 20 grams of oil.
It turns out that lubricant consumption can be considered acceptable if it does not exceed about 3 liters. per 10 thousand kilometers traveled. It is also important to understand that the consumption rate will greatly depend on the type of engine, its degree, etc.
For example, for many gasoline internal combustion engines, the norm is around 0.1%. On gasoline turbo engines, the consumption rate is noticeably higher. As for the standard, the declared lubricant consumption will be greater than any gasoline analogue and ranges, on average, from 0.8 to 3%. The indicated 3% is consumed by forced turbodiesels with two turbines, etc.
You can also separately mention rotary motors, which are particularly prone to lubricant consumption. Such units (taking into account their fully operational condition) consume about 1-1.2 liters of oil per 1000 km. mileage For reference, the manuals for different engines indicate that the norm for oil consumption for waste is 1 liter per 3 thousand km traveled, that is, about 3 liters per 10 thousand km.
At the same time, manufacturers also note that consumption directly depends on both the technical condition of the internal combustion engine and the operating characteristics of a particular vehicle (load on the unit, speed, etc.)
What determines engine oil consumption and how to reduce it
As mentioned above, oil is consumed in any engine, since the oil film on parts to protect against dry friction burns in the chamber along with the fuel charge. If we add to this the natural wear and tear of the internal combustion engine during operation, then lubricant consumption further increases.
However, it becomes quite obvious that 3 liters of oil per 10 thousand km. for a small car with an in-line aspirated engine this can be considered a high consumption, while for a powerful unit with a large displacement this is a completely acceptable figure. Practice shows that even if the engine begins to “eat” more oil than normal, it is more economically profitable to simply add lubricant than to immediately overhaul the engine just because of increased consumption.
The fact is that at many service stations, technicians prefer not to diagnose a separate cause of increased oil consumption, but immediately offer the owner to make major repairs. It is important to consider that such expensive repairs are not always necessary.
- First of all, lubricant consumption may increase due to oil leaking from the engine. In this case, it is enough to replace the gaskets and seals. As a rule, you need to pay attention to camshaft seals, etc.
In various situations, lubricant can flow along the external surface (leak out) and also penetrate into other systems. For example, if the crankshaft oil seal is at fault, a puddle may form under the car.
- If the oil is actively consumed in the engine by waste,... In this case, especially compared to a leak, it is much more difficult to determine the cause without disassembling the engine.
However, even in such a situation, you can try to fight the waste before agreeing to repairs. First of all, lubricant consumption depends on the operating mode of the motor. In other words, driving at high speeds leads to an increase in temperature and loads, the oil thins out, is less easily removed by rings from the cylinder walls, burns out, etc.
- It is also important to understand that the lubricant may not be suitable for the engine according to certain parameters. This means that you need to know which oil to choose for the engine and what features need to be taken into account.
If the engine is worn out, then at the same time you need to take into account the features of selecting oil for engines with high mileage. In a nutshell, the reduced viscosity material forms a thin film that the oil scraper rings cannot remove from the walls. If the lubricant is thick, then the film is very thick, and the rings cannot remove such a layer in full.
Taking into account the above, it becomes clear that you need to use the most suitable oil both in terms of tolerances and high temperature viscosity index. For example, from the list of recommended lubricants in the manual, you need to select a product with a higher viscosity compared to what is currently filled.
Each of the solutions has both its pros and cons, however, for a worn engine, in many cases it is possible to reduce lubricant consumption and.
- An increase in crankcase pressure also causes excessive consumption of lubricant. In simple terms, high crankcase gas pressure causes oil to end up where it shouldn't be.
As a result, the lubricant enters the cylinders through the intake, after which it burns in the engine along with the fuel. In such a situation, it is necessary to diagnose and clean the crankcase ventilation system.
- Problems with this also lead to lubricant leaks in the supercharger area, oil also entering the cylinders through the intake, etc.
The solution requires diagnostics and repair of the turbine. As a last resort, you can replace the turbocharger, and the lubricant consumption will also decrease.
What's the result?
Taking into account the above, we can conclude that the main reason for engine overhaul is the presence of significant defects and damage, as well as significant wear of parts and wear on the cylinder walls (scuffing, changes in geometry, etc.).
In this case, it will no longer be possible to eliminate the “guzzling” of oil only by decoking, replacing rings, valve stem seals, or switching to a more viscous lubricant. Typically, engines with such damage have low compression, start poorly both cold and hot, and significantly lose power.
During operation of the unit, knocking and extraneous noise may be present. As a rule, after disassembly and troubleshooting, the block needs to be bored/lined, the crankshaft grinded, etc. In other words, a major overhaul is needed.
If the engine is worn out, but operates normally, and the oil consumption is higher than normal, then you should not expect an immediate increase in lubricant consumption. The lubricant will be consumed more and more, but this problem will progress slowly.
It turns out that you add several liters of lubricant every 10 thousand km. will allow you to operate such a motor for more than tens of thousands of kilometers without major repairs (if no other breakdowns occur). At the same time, it is more cost-effective to add lubricant than to repair the engine.
Additionally, using a more viscous oil, replacing valve seals and cleaning the crankcase ventilation system will help reduce the overall consumption of lubricant and the cost of maintaining and servicing the internal combustion engine.
Read also
How to choose the right engine oil for an old internal combustion engine or an engine with a mileage of more than 150-200 thousand km. What you need to pay attention to, useful tips.
Then you have to add oil, you should spend time and determine the oil consumption:
Carefully pour oil exactly to the upper mark;
After 500 or 1000 km, use a measuring device to add oil and determine the consumption per 1000 km.
Some oil inevitably burns out during engine operation. Run-in engines consume about 0.2 liters per 1000 km. Oil consumption depends on the following circumstances.
Overfilling oil leads to increased oil consumption, since crankcase ventilation causes excess oil to enter the engine cylinders.
Low viscosity oil burns faster than high viscosity oil. Seasonal oil when hot becomes liquid like water, all-season oil remains more viscous. This quality, in particular, can reduce oil consumption when traveling over long distances.
Motor oil, especially all-season oil, which remains in the engine for a long time, needs to be changed more often.
Active driving style, in addition to increased fuel consumption, also leads to increased oil consumption. This is especially true when the new engine immediately receives full load.
During the break-in period, the engine needs more lubrication.
Oil leaks can occur in the following places:
Crankshaft and camshaft gaskets (these places are covered with a casing);
Gaskets on the cylinder head cover;
Cylinder head gasket;
Oil pressure sensor;
Oil filter gasket;
Oil pan gasket;
Rear crankshaft seal (oil appears at the junction of the engine and gearbox);
In places where engine components are worn, for example, due to defective valve stem seals, too much clearance between the valve stem and guide, incorrectly installed piston rings (if they were replaced), due to a defective or scuffed cylinder wall.
Frequent checks show that the engine is using little or no oil.
During short trips in winter, the oil level may not decrease at all or even increase. An increase in oil level means that it contains fuel or condensate. This oil noticeably loses its lubricating properties, so it is recommended to make regular long trips to “evaporate” the condensation. Check the oil level immediately afterward, as it may drop significantly due to evaporation of fuel or water! For intensive city use without long trips in between, you should select the appropriate oil change interval. The appropriate interval can be determined experimentally while operating the vehicle.
automn.ru
VAZ 2106 | Engine oil consumption | Zhiguli
Motor oil performs the primary lubrication and cooling functions inside the engine and plays an important role in keeping the engine in good operating condition.
It is normal to consume some amount of engine oil during normal engine operation. The following are the reasons for oil consumption during normal engine operation.
– Oil is used to lubricate pistons, piston rings and cylinders. A thin film of oil remains on the cylinder wall as the piston moves down the cylinder. The high negative pressure generated when the vehicle decelerates draws some of this oil into the combustion chamber. This oil, as well as some of the oil film remaining on the cylinder wall, is burned due to the high temperature of the exhaust gases during the combustion process.
– Oil is also used to lubricate the intake valve stems. A certain amount of this oil is sucked into the combustion chamber along with the intake air and burns along with the fuel. High exhaust temperatures also burn the oil used to lubricate the exhaust valve stems.
The amount of engine oil consumed depends on the viscosity of the oil, the quality of the oil and the driving conditions of the vehicle.
Driving at high speeds and frequently accelerating and decelerating consumes more oil.
A new engine consumes more oil because its pistons, piston rings and cylinder walls have not yet been ground in.
When estimating oil consumption, keep in mind that the oil may be diluted, making it difficult to accurately estimate its true level.
For example, if the car is used for frequent short trips and consumes a normal amount of oil, the dipstick may not show any drop in oil level even after driving 1000 km or more. This occurs because the oil is gradually diluted by fuel or moisture, making it appear as if the oil level has not changed.
The diluent ingredients evaporate when the vehicle is driven at high speeds, such as on the freeway, resulting in excessive oil consumption after high-speed driving.
One of the most important parts of proper vehicle maintenance is maintaining the engine oil at an optimal level so that the performance of the engine oil does not deteriorate. Therefore, it is very important to check the oil level regularly. Toyota recommends checking the oil level every time you refuel your vehicle.
automn.ru
Reasons for increased engine oil consumption
The problem of increased oil consumption very often worries owners of those cars whose mileage is already quite high after purchase or major repairs. But even on new cars, the engine often begins to consume oil beyond measure. To understand the reason for this, first let's look at a little theory on the matter.
For domestically produced cars, such as the VAZ 2106-07, or later models 2109-2110, the permissible oil consumption during engine operation is 500 ml per 1000 km. Of course, this is the maximum, but still, such consumption is clearly not worth considering as normal. In a good, serviceable engine, from replacement to oil change, many owners do not add a single gram. This is an excellent indicator.
So, below is a list of reasons why a car engine begins to eat oil too quickly and in large quantities. I would like to immediately note that this list is not complete and is made on the basis of the personal experience of many experienced owners and specialists.
- Increased wear of the piston group: compression and oil rings, as well as the cylinders themselves. The gap between the parts becomes larger, and therefore oil begins to enter the combustion chamber in relatively small quantities, after which it burns along with gasoline. With such symptoms, you can usually notice either heavy oil deposits or a black coating on the exhaust pipe. A major overhaul of the engine, replacement of piston group parts and boring of cylinders if necessary will help eliminate this problem.
- The second case, which is also quite common, is wear of the valve stem seals. These caps fit onto the valve from the top side of the cylinder head and prevent oil from entering the combustion chamber. If the caps become leaky, the consumption will correspondingly increase and the only solution to this problem will be to replace the valve stem seals.
- There are times when everything seems to be fine with the engine, and the caps have been changed, but the oil continues to fly away into the pipe. Then you should pay special attention to the valve guides. Ideally, the valve should not dangle in the bushing and the gap should be minimal. If the play is felt by hand, and especially strong, then it is necessary to urgently change these same bushings. They are pressed into the cylinder head and it is not always possible to do this at home, although most succeed.
- Oil leakage through oil seals and gaskets in the engine. If you are sure that everything is fine with the engine, and cannot understand why the oil is leaking, you should pay attention to all the gaskets, especially the pan. And also check the seals to see if they are leaking. If damage is found, the parts must be replaced with new ones.
- It is also worth keeping in mind that your driving style directly affects how and how much oil your engine will consume. If you are used to a quiet ride, then you should not have any problems with this. But if, on the contrary, you squeeze everything out of your car that it is capable of, constantly operate it at high speeds, then you should not be surprised at the increased oil consumption.
These were the main points that are worth considering if you suspect that your internal combustion engine's appetite for fuel and lubricants has increased. If you had a different experience, you can leave your comments below on the article.
zarulemvaz.ru
2.13 Oil consumption
Oil consumption
Some of the engine oil, while performing its functions, burns out. Thus, oil consumption is a completely natural process. Well-tuned engines consume 0.2 liters of oil per 1000 km. Audi calls the maximum allowable consumption 1.0 liters of lubricant per 1000 km. How much oil your Audi A4 consumes depends on the following circumstances:
- excess oil leads to greater oil consumption, because excess oil is blown into the engine through the crankcase ventilation;
- Thin oil burns faster than thick oil. When seasonal oil is heated, it becomes liquid like water, and its consumption increases accordingly. All-season oil stays thick; this entails lower consumption - this is especially noticeable on long trips;
- Multi-grade oil that remains in the engine for too long dilutes slightly, losing its highest viscosity grade, and the need for its addition increases accordingly.
- Abrupt driving at high engine speeds, in addition to increasing fuel consumption, also increases oil consumption. This is especially noticeable when the new engine immediately starts working at full load.
- During break-in, the engine needs a little more lubrication than usual.
- leakage. Check everything as described in the Engines chapter.
- defect in the engine itself; for example, defective valve stem gaskets, too large a gap between the valve guide and the valve stem, defective piston rings or their incorrect installation during repairs, damage to the cylinder wall due to wear or scuffing of the piston.
Lack of oil consumption is suspicious
In winter, when driving short distances, it happens that the oil level does not decrease from measurement to measurement, but even increases. There is no reason for joy here, since this means that the engine oil has been diluted by fuel or water condensate. These “additives,” which significantly worsen the lubricating qualities of the oil, must be “boiled down” by regular long driving so that the condensate evaporates. Then you need to immediately measure the oil level, since after evaporating the gasoline or water that got into the oil, its level will drop sharply! When driving exclusively in extreme city driving without intermediate long-distance trips, it is recommended to change the oil more often than at the intervals indicated above, for example every 3,000 km or every four months.
Oil consumption
Some of the engine oil is burned during the lubricating action. So oil consumption is a completely natural process. Well-run-in engines consume 0.2 liters per 1000 km; Audi calls the maximum allowable consumption 1.0 liters per 1000 km.
The oil consumption of your Audi 80 depends on the following circumstances:
- Overfilling the oil results in high oil consumption because the crankcase ventilation blows out excess oil.
- Thin oil burns faster than thick oil. Seasonal oil becomes liquid like water when heated, and consumption increases accordingly. Multigrade oil remains more viscous; First of all, those who drive long distances may notice less consumption of this oil.
- Multi-grade oil that remains in the engine for too long becomes thinner, the highest viscosity grade is “lost,” and the need for topping up increases accordingly.
- A harsh driving style, in addition to increased gasoline consumption, also increases oil consumption. This is especially noticeable if the new engine is immediately subjected to heavy loads.
- During break-in, the engine needs more lubricant.
- Engine leakage. Check according to the diagram described in the chapter Engines.
- Engine defect; e.g. valve stem seal (oil seal) defective, gap between valve guide and valve seal too large, piston rings defective or incorrectly installed
Zero oil consumption is suspicious
During winter operation over short distances, it may be that the oil level between measurements does not decrease at all or even increases. This is absolutely nothing to celebrate because it means that the engine oil is being diluted by fuel or condensation. This changing oil must be “boiled” during regular long trips so that the condensation evaporates. At the end of the trip, you should check the oil level, because it will drop significantly due to the evaporation of parts of gasoline and condensation! For extreme use in the city without intermediate long-distance trips, it will be better if you change the oil earlier than usual; perhaps after 3000 km or four months.
In winter, you should take into account the admixture of gasoline in the oil at about 2-3%, and thanks to the better dosed enrichment of the combustible mixture in our injection engines, when starting a cold engine, less gasoline gets into the oil than in old carburetor engines.
Correct oil specification
Since there is a risk of sediment forming in the oil sump with relatively long oil change intervals of 15,000 km, Audi has issued strict oil regulations.
- Regular mineral oil must comply with Volkswagen standard 50101 (VW-Norm 50101). In this case, it has sufficient cleaning properties to prevent the formation of sediment.
- Oils with good anti-friction properties reduce internal friction in the engine. They must comply with standard 500 00 (VW-Norm 500 00).
- Only if one of the oils listed above is not available, you can use all-season or seasonal oil of the API SF and API SG categories for topping up.
Oil viscosity
The fluidity of the oil, that is, its viscosity, must meet the requirements for use in a given engine. In this case, you should remember two criteria:
- The oil should not be too viscous, as the starter must be able to turn a cold engine, and the areas where the oil gets into the engine must be lubricated immediately after starting a cold engine.
- The oil should not be too thin, because at high temperatures and engine speeds the lubricating film may rupture.
SAE classes
The American Society of Automotive Engineers has divided oils into classes according to their viscosity.
Seasonal oil
These classes of motor oils begin with liquid winter (winter) oil SAE 5W, 10W, 15W through the intermediate stage SAE 20W/20 to viscous summer oils SAE 30, 40 and 50.
The cheapest motor oil used to be seasonal oil. For perfect engine lubrication, it must be filled with viscous or thin seasonal oil according to the time of year. Seasonal oil is almost impossible to find at gas stations or supermarkets today, but it is still often used in car parks. For use in the Audi 80, it is suitable (and this is the opinion of the manufacturer itself) only as a temporary solution in a hopeless situation.
All-season oil
The production of the multigrade oil used today is more complex, and therefore multigrade oil is correspondingly more expensive than seasonal oil. As a viscosity index improver, it contains long chains of molecules that “swell” when heated and lose volume again when cooled. In this case, the oil can “elastically” adapt to temperatures and cover many viscosity classes. SAE 15W-50 oil corresponds to a viscosity class of 15W at a temperature of –15°C, and to a viscosity class of 50 at 100°C.
The problem with mineral oil-based multigrade oils is that the chains of molecules that improve viscosity degrade over time, causing the oil to become less temperature resistant. For this reason, Audi does not allow the use of all-season oils of the SAE 10W-30 and 10W-40 classes in its cars during the warm season.
