Photo: Car oil is out Author: Konstantin Shirokun
It is indeed very important to fill your car with oil of the same brand and type. But what to do if the replacement period has come and there is no way to buy the necessary motor oil?
Read about what to replace the required grade of motor oil with in the RBC-Ukraine article.
How long the oil in a car engine will serve is determined one way or another by the car manufacturer. Most often, it determines the maximum mileage from replacement to replacement, but sometimes the moment is indicated by the car itself with an inscription or symbols on the panel. This applies to models whose electronics can calculate how severe the engine operating conditions were in the last period and by how much the standard replacement interval should be reduced in connection with this.
Why is this so important?
There are several basic factors that motivate the car manufacturer to set a particular service interval. In the case of modern engines, it is believed that the most important thing is to ensure the proper service life of the unit. The fact is that closer to the end of its service life, the oil gradually loses its qualities. All the additives that determine its characteristics are used up, and the worst thing is that the protective properties of the oil are reduced.
The standard, so to speak, interval, that is, calculated for ideal operating conditions, should be reduced if there were any complications in the operation of the car: prolonged engine idling, short trips without warming up the engine, towing a heavy trailer, trips on mountain routes, etc. On-board systems that can tell the driver the replacement period take these complications into account.
In addition, the same engine model for the markets of different countries may receive different oil change periods: 10 or 15 thousand km, 15 or 20 thousand km, 15 or 20 thousand km. It seems that marketing levers also work here, but the owner should still adhere to the manufacturer's recommendations.
How much mileage can you exceed on old oil?
No one will give you a precise figure. For at least two reasons: you need to know exactly how difficult the oil's operating conditions were and what kind of oil it was. After all, expensive premium brand oils have a larger reserve of additives, so under some conditions the engine may not even notice the mileage being exceeded.
And in principle, even a multiple excess of the mileage norm will not lead to an immediate accident, the engine will not break down or jam. But its most important parts will wear out more and more intensively, and the remaining resource of the engine may also be reduced several times.
What happens when an engine runs on old oil
In short, every extra kilometer of mileage on old, worn-out oil shortens the life of the engine. First of all, acids that form in it from moisture-condensate and crankcase gases harm the engine. The protective properties of the oil are reduced, because its alkaline number drops. Consequently, corrosive wear of metal parts develops, which is one of the main types of wear in ICE. Secondly, “expired” oil becomes increasingly thicker, which affects the nature of lubrication of parts and the starting qualities of the engine (primarily in winter).
Another large-scale age-related change is that due to the fuel that inevitably gets into the oil, the cleaning additives lose their effectiveness. And without them, the piston ring grooves become clogged with carbon deposits. As a result, the compression in the cylinders drops, the wear of the cylinders accelerates, even more oil will remain on their walls, and therefore there will be more carbon deposits… Thus, the problems progress in a race, as a result, the engine loses power, begins to consume excessive fuel and oil and marks the car on the road with blue smoke from the exhaust pipe.
Oil of another brand: can I add more?
It is not advisable, but when there is no other way out, then it is possible. It is important that the oil is of the same type (synthetic, semi-synthetic) and the same quality group (SM, SN, CH-4, CJ-4, etc.). It is also better not to deviate from the required viscosity, but a small deviation is acceptable (say, 5W-30 instead of 10W-40). However, all this advice loses its meaning if the level on the dipstick has dropped below the Min mark, and you need to drive on: in this case, you can add any oil from the motor category. Naturally, upon returning home, in all cases, the oil and its filter will need to be replaced with fresh oil.
Short
The shorter the oil life in the engine, the better for it. And the factory recommendations can also be adjusted towards reducing service intervals. But on the other hand, in a difficult situation, the replacement period can be overdue, and immediate trouble with the engine will not happen because of this. Nevertheless, if you value the future fate of your engine, do not overload it with high revs and excessive load at low revs on old oil.
Materials from Autocentre and Motor were used in preparing this article .
Let us recall that RBC-Ukraine recently reported why pedestrians are not always right.