It is not normal for any engine to burn oil. The reasons, solutions, etc. are described in the article.
The content of the article:
When an engine consumes oil, this is a reason to think about it. First, let's talk about additives, top-ups, etc.
Oil additives
According to most manufacturers, oil additives can literally cure your engine of anything, including high oil consumption. BUT no one has yet really explained how this is achieved. Reduce friction, extend engine life. Manufacturers of additives always indicate in advertising quantities that cannot be measured. This means that it is impossible to prove the fact of deception.
What we have in practice. Some oil additives actually create a certain layer on the parts, but this very layer has extremely low thermal conductivity. For example, for pistons this is fraught with sticking of the rings, more on that a little later. The remaining parts are not so susceptible to overheating, but it is definitely not good for the motor.
High oil consumption: reasons
We rule out a leak, this is not our case, it is not consumed by the engine, but simply flows out of it. Therefore, engine oil has only one path left - into the combustion chamber, where freedom awaits it in the exhaust manifold, or eternity in the form of coke.
In turn, there are two ways in which it can enter the combustion chamber: from above and from below.
Wear of valve stem seals
This is often a reason that is a consequence not so much of engine wear as of its old age. At their core, valve stem seals are rubber seals, which, like everything else of their kind, “dull” with age. Alas, this is the fate of each of them. This can only be cured by replacing the valve stem seals.
There are times when they become not an obstacle in front of the oil, but, on the contrary, a filler neck into which oil is constantly added. In addition, the cause may be a jammed valve. Some of the carbon remains on the seat, the other burns to the valve stem, after which it rusts the guide sleeve and the cap itself. This happens quite rarely, but, as they say, a stick shoots once a year.
Wear of oil scraper rings
Here it all comes down to the rings. The crankshaft lifts oil from the crankcase, sprays it along the cylinder walls, after which it must be removed by oil scraper rings. But this does not happen, part of it remains on the walls, and then, when the piston goes up, it is lifted into the combustion chamber. Of course, you can’t lose a lot in one stroke, but if you estimate the idle speed, then the crankshaft makes about 800 revolutions per minute, which means that 3200 strokes are performed, 1600 of which are upward movements.
Stuck piston rings are the cause of increased oil consumption. This problem is especially inherent in engines with poor heat dissipation, for example, those with shortened pistons. After the rings have settled, the situation becomes even worse because the oil cokes even more. Then they need decoking. Turbocharged engines are a separate matter, because a worn-out turbine is also an excellent funnel for pouring oil into the cylinders.
Conclusion
From all this it follows that oil burns can only be cured by repairs. In some cases, decoking will help, but this happens very rarely, because coked ones are found only at a decent mileage, and then repair is just a stone's throw away.
Video about the reasons for eating oil:
The increased oil consumption of some modern engines, or “oil burner,” as it is often called, is one of the most discussed topics on online forums. And this is not idle chatter. For example, on some Volkswagen TFSI engines (EA888) produced in 2009–2012 of the most common types (1.8T and 2.0T), with a mileage of 60 thousand to 120 thousand kilometers, oil consumption for waste begins to increase sharply - up to a liter and a half per thousand kilometers.
We will tell you about the 1.8T turbo engine, which had very indecent consumption: 400 ml of oil per 100 km. Not a thousand kilometers, but a hundred! And this is not an isolated case.
AUTOpsy SHOWED
The engine malfunction revealed two critical, in our opinion, circumstances.
First: the oil scraper ring is completely clogged with black deposits of unknown nature. The same deposits were observed on the second sealing ring. They were present both on the outer side of the ring, adjacent to the cylinder, and on the inner side, where the expander spring is located. Its coils were practically caked due to this dirt, and therefore the expander was inoperative. It's funny that the coils of the expander spring are imprinted on the cast iron of the ring body. This usually does not happen because the spring moves relative to the piston groove. These prints clearly indicate that the ring is motionless. Which means it doesn't work.
Second: the spring of the oil scraper ring expander, which should ensure its pressing against the cylinder walls, has noticeably lost its elasticity. This happens when it overheats. This part is heat-fixed, that is, it receives its elasticity in the process of appropriate heat treatment. Its overheating above the thermosetting temperature leads to the so-called release of the spring, that is, to a loss of elasticity.
Let's discuss further. In a working engine, when the piston moves up and down, the rings also periodically move from the lower end of the groove to the upper. This is called ring repositioning. The shifting moment is determined by the direction of movement of the piston and the pressure difference acting on the ring. But if the gap in the groove itself is completely filled with oil, then when the ring is moved from the upper end to the lower end, part of the oil is pumped upward into the combustion chamber (the so-called pumping effect).
During normal operation of the rings, only traces of oil are observed in the grooves. The oil film sits on the cylinder wall - the pumping effect does not appear. But if there is no drainage, the rings begin to pump oil into the cylinder. This is exactly the case: the tiny drainage holes are clogged with dirt!
Stagnation of oil in the grooves in the absence of drainage and elevated temperatures leads to accelerated aging and decomposition of the oil - this is how the very black deposits that we observed when opening the engine are born.
Another possible reason for a sharp increase in oil loss is a non-working oil ring expander spring. This ring is the most important element of the combustion chamber sealing system of a piston engine. Its task is to regulate the supply of oil to the area of the compression rings, which take on the main gas load.
If this regulation (i.e. oil restriction) stops working, then the thickness of the oil layer left by the first piston ring on the cylinder walls increases sharply. With it, oil consumption for waste also increases.
ERROR OR ENVIRONMENTAL PAYMENT?
What is the reason for this oil consumption? And what is this - a design feature of the motor or an accident?
When you open such an engine, the miniature pistons immediately catch your eye ( photo 4). This is a modern trend in the design of high-speed engines: designers are trying to lighten the piston as much as possible - in order to reduce the inertial loads on the connecting rod and crankshaft, as well as to reduce the force of pressing the piston against the cylinder walls. All this helps to reduce friction losses in the engine, leading to an increase in its mechanical and effective efficiency. The goal is to reduce fuel consumption and, most importantly, the content of carbon dioxide CO 2 in the exhaust gases.
As a result, the piston turns out to be “short”. If previously it was accepted that the height of the piston should be no less than the diameter of the cylinder, now this rule has been abandoned. Moreover, a T-shaped piston design is now used, in which the supporting part of the side surface is reduced as much as possible - only segments of the side surface of the throne (skirt) remain in a plane perpendicular to the piston pin axis. This also reduces friction losses. But the negative effects of reducing the piston size are obvious. With increasing loads in a forced engine, a smaller amount of iron that receives them works under more severe conditions. The temperature of the piston increases, and so does the voltage in it. The consequence is a decrease in service life and reliability. And, as a special case, the possibility of overheating of the piston group.
That's not all. To reduce the temperature of the piston, it is cooled by a stream of oil from nozzles embedded in the main oil line of the engine. In the engines under consideration, these injectors have valves that open at a pressure exceeding 0.18 MPa (in new versions - 0.25 MPa). This is done because when the injectors open, the oil pressure in the line drops, and this can deprive some of the bearings of lubricant. But oil pressure depends on two parameters - the engine oil temperature (the higher it is, the lower the pressure) and the crankshaft speed. This means that in the most unfavorable operating conditions of the engine - at high ambient temperatures, low speeds and high load - the pistons are not cooled! After all, the injectors are closed at low pressure!
In short, the engine can easily be killed if you load the car to capacity on a hot summer day and drag it in high gear up a long climb.
Another feature of this Volkswagen engine is the size of the piston rings. They are unusually narrow. In addition, the height of the first ring is only 1.0 mm, the second one is 1.2 mm, and the oil scraper ring is 1.5 mm! This seems completely strange - after all, neither in our GOST standards, nor in the German DIN, nor even in the catalogs of piston rings from leading companies, we found rings with a height of 1.0 mm with a cylinder diameter of 82.5 mm; It turns out this is some kind of special order.
What does this mean? A ring with such dimensions reduces its mechanical strength. This is especially important for the oil scraper ring box. To compensate for the decrease in strength, the ring manufacturer went to reduce the already small drainage holes in it. Hence, there is an increased risk of their coking and complete loss of drainage.
Another important aspect. For normal operation, the piston ring must be pressed against the cylinder wall - otherwise there is no seal. The ring is pressed by the pressure of gas forces, which is sufficient only during the compression and expansion strokes, that is, less than half the duration. The rest of the time, the force of its own elasticity works. But the smaller the ring size, the less pressure it can create on the cylinder wall. And this is a parameter enshrined in regulatory documents: a lot depends on it. By the way, there is such a thing as piston ring flutter: a certain oscillatory process in which the ring operates unstably, does not seal “through the gas” and drives the oil upward. So, reduced radial pressure is one of the factors that contributes to the occurrence of this very flutter.
But that's not all. Instead of the usual first o-ring, we saw a so-called torsion bar, which has a tricky pattern on the inner surface. Such a chamfer creates a different moment of resistance in different sections of the ring, and this leads to its “twisting”, which increases the local specific pressure on the cylinder wall. But even in theory they don’t do that! The installation of torsion rings as the first rings was at one time considered unacceptable due to their negative impact on the wear rate of the first piston groove.
A “skewed” ring creates increased contact pressure not only on the surface of a durable steel or cast iron cylinder, but also on the groove in the piston - soft and pliable, because the piston is made of an aluminum alloy and is also very hot.
We look carefully at the piston of the disassembled engine. Yeah, that’s right: to compensate for this negative, the first groove is cut into a special cast-iron wear-resistant insert ( 3 ). But such an insert, while protecting against wear, disrupts the normal cooling of the piston - after all, the thermal conductivity of cast iron is five times less than that of an aluminum alloy piston, and such an insert interferes with the flow of heat flow. This is an additional way to overheat both the piston and the oil scraper ring.
And finally, one more “discovery”. Usually, special through holes are drilled in the piston to drain oil from the oil scraper ring operating area. But even here a surprise awaited us. Not only are the drainage holes tiny, there are only four of them ( 5 )! The pistons of similar engines, as a rule, have at least eight of them ( 6 ). And once upon a time, instead of holes for drainage, slots-windows were made. Not the best solution in terms of piston strength, but the drainage always worked.
The small number of holes, coupled with their miniature size, impairs oil drainage, and this eventually leads to coking - similar to drainage in the oil scraper ring itself. We told you at the beginning of the article how the work ends in the absence of drainage.
Why was this done? Most likely, to reduce stress in the area of the groove for the oil scraper ring. It is clear that each hole is a stress concentrator, and they are already high there. By removing half of the drainage holes, we got rid of half of the concentrators - it became easier for the piston. But nothing is given for free - in the end you got what you got.
FOR WHAT?
Why did the designers create a piston group, the main solutions of which contradict the established practice of engine design? We can only assume: in order to meet the requirements of the current Euro-5 standards and the new Euro-6 standards for toxicity and CO 2 content in exhaust gases. The point is to limit the content of so-called non-fuel residual hydrocarbons, which are produced by burning motor oil: reducing waste is strictly linked to toxicity. This is partly why a torsion ring was taken as the first ring, which is usually used as an oil seal.
The low height of the piston rings and trunk allows for a reduction in specific fuel consumption. This is important both in itself and as a factor limiting the release of CO 2. However, the service life suffers: the specific loads on the piston, rings and cylinder walls increase, and therefore the wear rate inevitably increases. But for a modern engine, resource is no longer the main thing.
So, with a high degree of probability, the cause of the defect can be considered a non-optimal design of the engine piston group, which increases the possibility of oil overheating in the area of the piston grooves and worsens the drainage of engine oil from the oil scraper ring into the engine crankcase. All this contributes to a sharp increase in oil flow into the combustion chamber.
They will object to us - they say, not all Volkswagen engines suffer from a similar feature. Yes, to start the “oil burner” mechanism, several circumstances must coincide: the engine was once overheated, plus frequent short trips, plus the tetanus of traffic jams, and also unstable quality of engine oil, clogged radiator honeycombs... Therefore, the “oil burner” is not a system , but a floating defect. But this does not make it insignificant.
FUCKING CONFESSION?
Are Volkswagen engineers aware of the problem? They know! The Germans even sent out several notices to their official dealers with recommendations to correct the situation. The last point in them: if, supposedly, reflashing the controller and eliminating problems with crankcase ventilation do not help, replace the piston with a new, optimized one. Its rings are more familiar: the height of the first has increased to 1.2 mm, standard for engines of this class, the height of the second has also increased to 1.2 mm, and the oil scraper ring has increased to 2.0 mm. By the way, in new (starting from 2012) motors, a second O-ring 1.5 mm high is installed in the basic version. That is, the company, in fact, returned to the configuration that is typical for engines produced before 2000.
The width of the rings has also increased. This is important, since the moment of resistance of the ring, and therefore its rigidity, depends linearly on the height, and the dependence on the width is cubic! And if in the old version of the first compression ring the measured elastic force was less than 10 N, then in the new one it returned to the usual 15 N for engines of this size. The same is true for the remaining rings. The increased height of the oil scraper ring has improved drainage. The pistons changed accordingly. The repair also entails replacing a set of connecting rods: they are not interchangeable with the old ones - for some reason the diameter of the piston pin has been increased by 1 mm.
By the way, attempts to order old versions of miniature piston rings and pistons for them for additional research were unsuccessful: they are no longer in warehouses! New cars are equipped with optimized rings and pistons, and Volkswagens since 2012 have virtually no problems with oil leaks. But cars produced in 2009–2012 are at risk. And no guarantee applies to them anymore.
At dealers, the cost of such a repair kit, including replacement work, exceeds 150 thousand rubles! You have to pay for strange design solutions out of your own pocket.
What if it's cheaper? There is a solution. The standard set of miniature rings is being replaced with another one - with sizes close to those that have gone into production since 2012. In this case, the serial oil scraper ring with a spring expander and a box-shaped housing is replaced with a so-called three-element one, consisting of two scrapers and a spring expander. The old pistons are used, but the grooves for the piston rings are bored to fit the new rings. The connecting rods also remain old. By the time this article was prepared, more than a dozen engines had been cured in this way. The result is positive: the “oil guzzling” has stopped. Moreover, such repairs are three times cheaper than those prescribed in the notice from Volkswagen.
To 260 thousand km. our Volkswagen Passat B5 ANB 1.8T (turbo) began to critically eat up oil. Oil consumption was at first 2.5 liters per 9 thousand, then 3 liters. per 10 thousand. Over 4 years of ownership, the usual consumption, if you do not turn it up to 5 thousand revolutions, was 1 liter per 10 thousand km. The car began to smoke after 3 thousand revolutions and, when idling, sometimes spit out a cloud of bluish smoke.
In specialized respected services, they critically and persistently offered a full engine capital, saying that the rings were worn away, and the valve stem seals on a 20-valve engine were so small that if they were missing, it would not consume more than a liter. The cost of such capital was estimated at 70 thousand rubles (and even more - an autopsy will show). They refused to change the valve stem seals separately. When the car costs 250 thousand and there are delayed problems with other expensive units, this is not an option. But it was not possible to buy a fresh car in better condition for 100 thousand with the same parameters and much better condition.
And so, after talking with the men, we began to rule out the causes of oil consumption one by one. We checked the turbine - it whistles, but there is no oil flowing into the pipe yet. Next, they advised us to measure the compression - if there is no standard or significant variation, then the oil scrapers are simply stuck (of course, there is a risk of oil compression, but we neglected this). Measurements showed 11.5-11.5-12-12 (of course not super smooth, but quite normal for a 16-year-old car). There is oil in the glasses of the spark plugs (thanks to Transmissions and Motors, who install shitty Chinese gaskets - and also repair engines). There is a lot of maintenance ahead and we decided to stop at replacing the valve stem seals; they are still within easy reach when the face and part of the attachments are removed.
We found the master Nikolai from "Che Service", the cost of replacing the valve stem seals with removing the muzzle was only 12 thousand rubles. (bonus: replacement of timing belt, spark plugs, damper - the biggest maintenance costing from 6 thousand rubles) + parts. Everything was done accurately, for the agreed amount. At the moment, the mileage has already reached 7 thousand km, I keep the oil level to the maximum, topped up with about 600 g. At the same time, it turned up to 5 thousand revolutions on the highway, overtaking trucks.
Thus, our Passat B5 (VW Passat B5 1.8T ANB) eats up oil when it reaches 260 thousand km. mileage is 3 liters per 10 thousand km, with normal compression in all cylinders, it is trivial due to hardened oil seals. Replacing them made it possible to get rid of the bluish haze and significantly reduce oil consumption. Moreover, the cost of these works is disproportionately lower than the full capital cost. Of course, it will not completely solve the problem, but even on this engine oil consumption is allowed within the limits of at least a liter per 10 thousand km. mileage...
“How long will a 1.8 TSI engine last, which consumes 1 liter of oil per 500 km? I have a Skoda Superb, bought from a showroom. The engine took oil from scratch, but within reasonable limits - about 0.1 liters per 1000 km. The official service responded to complaints that this is normal, as it should be. There is enough power, fuel consumption is normal, only the oil... Only when accelerating, when the pedal is completely pushed to the floor, can you see a little bluish smoke behind the car. At 82,000 km the failed ignition coils and spark plugs had to be replaced.
I tested various oils. First 5W-30, then 5W-40. However, oil consumption was consistently high. The car was purchased in 2009, which means it is no longer under warranty. I don’t like replacing rings, pistons and connecting rods at my own expense, since the cost of such an operation is very high,” the owner of a Skoda Superb shared such lamentations on one of the automobile forums. Similar messages can be found from owners of Volkswagen, Audi and Seat.
Or here’s another post: “I have the same problem. The car has a mileage of 107,000 km and has been in service since yesterday. The turbine does not take oil (checked). He asked me to disassemble the engine and clean everything inside: rings, seals, etc. I add that the engine consumes 1.3 liters of oil!”
These are just two of several hundreds, if not thousands, of VW car owners who complain about defects in TSI and TFSI engines. We are mainly talking about engines with a displacement of 1.8 and 2.0 liters. Although, in accordance with the position of WV, if such a problem exists, it only applies to 2.0 TSI/TFSI engines. Moreover, the number of such cases is growing at an alarming rate from year to year, but the manufacturer does not change his view. It goes something like this: “We've built millions of cars with these engines. The problems you mention only apply to individual instances. These are not even percentages, but their thousandths. There can be no question of any constructive miscalculation. Each such case is considered individually.”
But is this really true? Or is this just deferring repairs so that the owner can solve the problem at his own expense after the warranty expires, saving the manufacturer from unnecessary costs?
It turns out that in fact, Volkswagen had already made a diagnosis and in 2011 upgraded some of the components of the problematic engines. Despite this, no mass service campaign was ever organized, leaving the owners with the only choice - to repair the engine at their own expense. It is possible that the German concern was afraid of the large number of customers who would want to take part in the action, although their engine was spared the problem.
Before the onslaught of work, official services raised the price tag. The estimated cost of a comprehensive and effective repair is approximately $5,000. Too much for a car that costs only 2-3 times more.
Some owners of VW Group cars, trying to solve the mystery of the disappearance of oil by touch, together with independent mechanics, threw away thousands of dollars to repair heads and replace: valve seals, various seals, gas distribution mechanism, turbines and other things.
And yet, several people decided to disassemble the lower part of the engine. The inspection showed that the cylinder walls, with a mileage of about 100,000 km, show no wear - the parameters are within the tolerances provided for the new engine. Further examination revealed that the TSI engine pistons were not only short and light, but also had an oil ring that was too thin. It is these rings that are responsible for getting oil into the combustion chambers. It is normal for a small amount of oil to leak through. But 0.5 liters per 1000 km is already a lot. With such oil consumption, many owners of old cars are already rushing to the service center for major engine repairs.
The standard set by the manufacturer (0.5 liters per 1000 km) can rather be considered as a desperate protective measure against annoying and angry customers. High oil consumption is harmful to the environment, the owner’s wallet and the engine itself. Amid the problem, some are trying to switch to cheaper brands of oil, which further aggravates the problem.
“At the car service center, all the oil was drained from the engine, then the prescribed amount of new 5W-30 oil was added. After 115 km, the service center drained all the oil again and weighed it. After calculations, it turned out that the engine takes 0.465 liters per 1000 km, and this, as you know, is within the normal range.” This is how one of the owners of a Volkswagen car describes the method for measuring engine appetite.
A set of piston rings is inexpensive - a few hundred dollars at most for a top quality product. If we were talking about a regular replacement of rings, then all the problems could be solved relatively quickly. In the case of the TSI, replacement was not possible because VW realized that the too thin rings were ineffective and stopped producing them. Instead, he proposed a new piston model, equipped with normal rings, but not compatible with the old connecting rods.
On the left is the old piston, on the right is the modernized one.
The repair will require replacing all pistons and rings ($900), connecting rods ($800), bearings ($60) and numerous parts. The total bill for parts will be around $2,000! Customers of Audi, Volkswagen, Skoda and Seat will feel deceived. Not only did they purchase a car with a defective engine for which it was impossible to purchase the original parts, but they were also forced to purchase upgraded parts at absurdly high prices - above market prices!
Theoretically, repairs at a good independent auto repair shop with original parts purchased from official VW dealers will cost about $2,500. But in practice, it turns out to be much more expensive, because, among other things, it is necessary to replace the timing belt (there are also problems with it) and prepare the crankshaft for installing new bearings. All this costs a lot, but is still cheaper than in the official service.
However, there are cheaper ways to reincarnate rings. Savings occur due to the installation of old pistons and connecting rods. To do this, the block is disassembled, and in defective pistons the size of the oil scraper ring groove is increased to “normal”. Then a new ring is installed.
The total cost of such repairs is much lower - only about a thousand dollars. And the epic with oil consumption and blue smoke comes to an end! But no one knows how long such an engine will last. After all, no one tested the strength of the pistons, which were thinned during the refinement process. The pins and connecting rods remain old. Meanwhile, VW changed the piston design in TSI engines in 2011. Probably not without reason, these parts were strengthened.
So why doesn’t the German concern cover the entire cost of repairing faulty engines? It does not do this either in Europe or in the USA, where the concern had the misfortune to face a collective complaint from the owners of the Audi A4, A5 and Q5. In September 2014, the German company lost the civil case. Now each of the potentially affected 126,000 customers can contact VW representatives with a request for free repairs. To benefit owners, the engine warranty has been extended from 4 years/50,000 miles (80,000 km) to 8 years/80,000 miles (128,000 km). According to VW/Audi representatives, this is a completely different story, since the engines on the American market are structurally different from those sold in Europe. The argument is quite dubious, just like the rings in TSI engines.
