Oil consumption in the internal combustion engine during operation is a normal phenomenon for any car. However, it is very important to understand how quickly the level drops and how much oil the engine spends. Let’s understand what consumption is normal, and when it turns into a real “oil spoilage”, what affects it and when it is worth worrying.
Where oil can go
If the engine consumes oil, then where exactly? There are two options. Either it leaks out, for example, through blistered oil seals or gaskets, or it burns in the engine. There is no escape from the latter. Oil, among other things, lubricates the pistons, rings and cylinder walls. When the piston moves downward, the oil ring cannot remove all of it, and a small portion is inevitably burned with the fuel. In addition, oil can seep into the combustion chamber through valve seals (caps). Finally, lubricant can be burned off by entering the manifolds through the turbocharger, where the bearings require oil.
What the oil flow rate should be
This parameter is individual for each car. For example, some Volkswagen motors have such an excellent “appetite” that they require refilling up to 1 liter of oil per 1000 kilometers. And the German automaker does not consider it a problem or a malfunction.
Of course, most motors have a more modest consumption. If the engine has not yet passed the first hundred thousand kilometers, it is normal when it spends about 100 grams per 1000 kilometers. That is, if you change the oil once every 10,000 kilometers, it will not need to be topped up. The difference between the Min and Max marks in engines of average working volume is just about 1 liter, that is, the level will not fall below the minimum.
Internal combustion engine oil consumption depends on the type of unit. In particular, turbo engines usually consume more oil than “atmospherics” for the reason described above. Also, the consumption is affected by the manner of driving. If you like to crank the engine to high revolutions, get ready to refill oil regularly – in such modes more lubricant is burned.
The oil level should be measured not earlier than 10 minutes after stopping the engine. This time is necessary for the lubricant to flow from all channels and parts into the oil pan, where the dipstick is inserted.
Why oil consumption increases
All the features that we have described above are a given. But it happens that the level can fall below the minimum, although before refilling was never required. If there is a so-called oil glut, the reasons are not always obvious. Here are what they can be:
Wear of sealing elements
In this case, the oil simply leaks out through leaking connections. It is easy to check whether everything is in order with oil seals and gaskets: it is enough to inspect the engine from above and below. If you can see sweat or wet dirt somewhere (road dust quickly adheres to leaked grease), there is obviously a problem with the seal. Sometimes when leaks occur, the motor “eats” oil quite actively.
Wear and tear on the oil caps
Just like gaskets or oil seals, valve oil caps also “get stale” over time – they lose elasticity and can not work effectively. This is another reason why the engine “eats” oil. The only way out of the situation is to replace them with new ones.
Cylinder and/or piston ring wear
In this case, the oil rings stop coping with their duties, leaving more oil on the cylinder walls, and it burns with the fuel. In addition to mechanical wear, it is possible to “lay” the rings, when they lose performance due to heavy fouling.
Incorrect oil viscosity
We have already explained more than once that you should select oil according to the manufacturer’s recommendations, and not on the basis of your own experience with other cars. Designs can be different – some are recommended 0W-20, others 15W-40. If you pour oil of a lower viscosity, its consumption will be greater. And if there is oil burning, the reason may be its wrong choice. By the way, even within the same viscosity different oils may have different consumption. But, of course, within the permissible limits.
Malfunction of the ECG system
One of the obvious signs of a malfunction of the crankcase gas ventilation system is increased oil consumption. Depending on the nature of the problem, it can either be squeezed out through the slightest looseness, or drawn into the cylinders together with air. That is why a seemingly serviceable motor “eats” oil, and you have to refill it again and again.
What signs you can determine the increased consumption
If this is your car, it is enough to simply check the level regularly. But how to understand whether the engine has a tendency to increased oil consumption, if, for example, you are just buying a car? It is worth paying attention to the following signs.
Smoke exhaust. If the smoke is blue in color – this is the most obvious sign of problems. Do not confuse it with white vapor when starting in subzero temperatures – this is just condensate evaporating. You can run your finger along the inside of the exhaust pipe. If the deposits are oily, there is likely to be increased oil consumption in the engine (and the engine itself is far from being in perfect condition).
Smoke from the oil filler neck. You can open the lid on a running engine and check if the same smoke from there. Its presence may indicate at least a problem with the crankcase ventilation.
Black oil on the plugs. This should not be the case. Remove any plug and look at the electrodes. If the deposit is black but dry, it may indicate over-enrichment of the fuel mixture. And if it’s “greasy” (wet), there’s an oil problem. There should not be oil traces on the plug threads.
The engine “eats” oil, but does not smoke. In this case it is worth looking for a leak, sometimes it is difficult to see – for example, because of the crankcase protection.
How to understand the “scale of the disaster” with oil consumption
Let’s assume that you found too high oil consumption in the engine, errors in the choice of lubricant, and there are no leaks. How to understand how large-scale repair is needed?
First of all, compression is usually measured. If it is in order, it means that the matter is most likely in the oil caps. They can be replaced inexpensively at the service. But if the compression is low, it is the fault of the piston rings, which leave too much oil in the cylinders. Sometimes in such a case it is possible to get by with “little blood” – to perform engine de-scaling from carbon deposits with the help of special preparations. But it cannot be excluded that it will be necessary to change the rings, or even do a complete overhaul of the engine.
Summarized results
- A certain amount of oil is burned when the engine is running, it is unavoidable.
- Oil consumption depends on the design of the engine: for some and a liter per 1000 kilometers is considered normal.
- The consumption may increase due to the appearance of leaks, “laying” oil piston rings, poor operation of oil caps or crankcase valve.
- Signs that the engine is actively consuming oil are blue smoke from the exhaust pipe and filler neck (with the cap open), as well as oily deposits on the electrodes or plug threads.