Everyone knows that engine oil in ICE performs extremely important functions. The main ones are cooling parts and their lubrication. Cooling occurs due to heat transfer from heated parts into a pallet of the crankcase or oil radiator. And lubricants are associated with a thin oil film on the details. It is due to it that the fuel surfaces do not come into contact and are not wearing, as well as protected from overheating, melting and scoring.

In the process of operation of the engine, the properties of the engine oil may be violated as a result of four main reasons:

1) Faults of ventilation, cooling and fuel feed systems,

2) the car works with some special modes that affect the condition of the oil,


4) The engine is flooded with an oil that does not correspond to the vehicle manufacturer specifications.

Let us clarify some reasons.

Faulty engine ventilation system?

However, the operating conditions of the engine are a separate question. Take, for example, cold weather. At this time, short periods of starters are rapidly, without complete engine warming. Or long modes of engine operation at idle. It turns out that with a small car mileage, the engine operation turns out to be excessively large. Such a mode of operation is called a typhell. At the same time, the oil is exposed to aging, while according to the actual run, the execution period is not yet.

And short starts, and typing leads to the fact that the oil loses the detergent properties. As a result, mase descendible deposits are formed on the inner walls of the engine. They clog oil — and it can be sedimed in the pallet of the crankcase. A particularly large layer of deposits sticks on the surfaces of the cylinder head and under the valve lid. In the most difficult cases, the piston rings in the grooves of the pistons occurs.

As for additives to the oil, there is not so simple here.

If in the engine there are signs of deterioration of the oil properties, and it is established that some «drugs» were added to it, then it does not mean that the oil is spoiled by supplements. In this case, it is necessary to consider the reverse version — when additives flooded to eliminate some kind of engine malfunction.

As the composition and fuel property affect the process of aging oil

The most frequent factor of fast aging oil is inappropriate fuel. What it is?

In order for gasoline to have a certain octane number, it is enough to add special additives to it — anti-knock. The most common anti-knock is a chemical methyltretile ether (MTBE). In addition to it, Iopentanes, Isoocan, Neohasane, Benzene, Toluene, acetone, ethyl alcohol, etc. are used, etc. All these substances can be called permissible additives.

However, fuel producers are unclean on hand, in addition to the allowators permitted, may well be elevated to gasoline and others, even cheaper analogues. So receive inappropriate fuel.

For example, in the production of synthetic rubbers, products are formed in which there are many unshakable hydrocarbons. They are added to gasoline, increasing the octane number and at the same time reducing the cost of fuel. These same hydrocarbons contribute to the fact that nitroesters are formed during the combustion of fuel, which are then reset into the engine crankcase and already there at high temperatures are converted into soap thickening oil up to the total fluidity loss.

Another example of inappropriate fuel. Gasoline contains excessively a lot of ethyl alcohol — up to 20%, with a standard no more than 5-10%. The alcohol is oxidized, forming substances that interact with engine oil. And the trouble occurs — the additive, thickening oil, falls into a precipitate. This case is characteristic of modern engines with low-grade (energy-saving) oils having a viscosity over SAE 5W20 or 0W20 when operating in winter time (with frequent cold engine launches).

We are looking for a DVS malfunction associated with oil quality

It is useful to list specific signs of the fact that it is the change in oil properties that caused the engine malfunction.

This is primarily:

• the appearance of excessive sediments on internal details,

• The formation of precipitate and particles scoring the grid of the oil worker.

However, in itself, the deviation in the properties of the oil is not at all necessary necessarily causes the engine malfunction — this is possible only when there is a connection between damages on the details and deviations in oil properties. To find such a connection, changes in oil properties, depending on the effect on the engine, we divide into 2 groups — general and local.

General changes in oil properties are:

• appearance in the volume of oil sediment,

• a significant increase in viscosity — up to the loss of fluidity,

• Strong nagar formation and maze deposits on the walls.

General changes in properties reduce oil supply to rubbing pairs. For example, gasoline pairs that have passed through the sealing belt of the pistons, when mixing with crankcase gases affect oil and start the early triggering of additives. Oil sharply thick, normal lubrication and bearing cooling are broken. A sediment is formed closing the oil grid.

Local changes in oil

Interestingly, on a preliminary inspection of a faulty engine, it is not always possible to establish signs that the oil could somehow affect the malfunction. However, starting to diagnose the engine breakdown is useful with taking oil and fuel sample. And samples should be saved in the case when suspicion of the connection of the properties of the engine malfunction will be confirmed.

If necessary, the sample of motor oil and fuel is transmitted to specialized chemical laboratories. In the study of motor oil, there is usually viscosity at 40 ° C and 100 ° C, the viscosity index, the flash temperature, an alkaline and acid number, the content of various elements characterizing the additives, weathered parts and contaminants. In addition, the main additives included in the oil, as well as foreign substances and pollution. The measured parameters are used to establish the reason for changing the properties of the oil and its mutual influence on the operation of nodes and parts.

Similarly, fuel can be studied — determine the octane number, evaporation, the composition of the fuel.

Often in practice there are no signs of an engine oil with abnormal properties. Or they cannot be found. In this case, the study of oil or fuel is useless simply because the results will not be applied to, and they do not talk about anything.

For example, observe signs of destruction of the crankshaft bearings. In this case, it makes no sense to explore the composition of the oil on the content in it additives. And all because no additives affect the operation of the sliding bearings, but the supply and viscosity of the oil. But on the malfunction of the valve mechanism, neither viscosity or additives are often affected.

The result of analyzing oil and fuel properties by itself does not indicate the cause of the fault, but can confirm the version extended on the basis of the study of signs of damage to parts. In other words, looking for a fault, producing chemical analysis of fuel and oil, is completely useless. However, if there are signs of any malfunction, the analysis may confirm it or, on the contrary, refute. And this is not only the difficulty of research related to engine oil, but also the manifestation of a kind of «cunning» of fuel, affecting the oil literally «from behind the corner» …

Article author:

Alexander Khrulev

Motor Center «AB-Engineering»

High-quality professional engine repair with any malfunction

Tel. +7 495 545 6936