Do I need to change the oil in a BMW automatic transmission?
Quite a lot has been written about the need to change the oil in an automatic transmission (automatic transmission) in many car manuals. All drivers know about it. But, for some reason, about 30% of our customers arrive late for a replacement. In this article, we recall once again that the oil in the box should be changed every 60–80,000 km or 3 years of operation.
Why is it necessary to make a replacement?
Modern oil, which is used in automatic transmissions, is the most complex high-tech compound. It provides effective lubrication at high speeds of rotation of the gearbox mechanisms. The complexity of effective lubrication under such regimes has long worried engineers and chemists. The point is that in order to ensure the lubrication of parts at high speeds, the oil must have high fluidity, and with an increase in fluidity, the oil has time to penetrate between the gears, but the lubrication efficiency decreases. And a thinner layer does not provide sufficient film thickness, and metal surfaces interact, especially under heavy loads. This problem still remains unresolved for many oil manufacturers. They managed to solve the problem partially by finding a middle ground. And it was only the world’s leading concerns that managed to completely eliminate this shortcoming, which found finance and managed to solve this difficult task. Their oils are also highly fluid and can maintain a sufficient oil film thickness at high and low speeds.
That is why box oil should only be purchased from brands recommended by the BMW manufacturer.
But only such oil has a drawback – it cannot be used for a long time.
There are several reasons for the loss of properties:
Oil aging over time. After two winters, when the oil is subjected to repeated freezing and thawing, the destruction of the very polyatomic oil molecules that ensure its efficient functioning occurs. After reaching the critical value, the oil can no longer reduce friction to the established standards, and the wear rate of parts begins to increase.
Loss of oil properties during operation. When an oily fluid is placed between moving parts, especially between gears, it is subjected to very high local pressure between the mating surfaces. The high pressure and high temperature in these small areas is very bad for the oil, resulting in broken molecules. Of course, there are many molecules in oil, and it will not be possible to destroy them all. But over time, the percentage of destroyed molecules reaches its dangerous value – the oil stops working normally. This happens at the turn of 60 – 80,000 km. The absence of a hard oil change period is due to the nature of driving. The smoother and more accurate the style, the higher the interval, the more “harsh” driving style, the shorter the interval.
Oil clogging with wear products. No matter how effective the oil is, unfortunately, it is impossible to reduce the contact between metal surfaces by 100%. There will always be some friction left. As a result of this, microscopic particles are separated from the metal, which enter the oil. Their number is small at first, but over time it becomes more and more. And they reach the threshold value just in time for replacement.
These are the main reasons. There are also secondary ones, concerning the chemical processes themselves that occur in the oil under the influence of various factors, but their influence on the quality is minimal.
Summing up what has been said, we note that changing the oil is a mandatory procedure that must be carried out on time. Failure to comply with such requirements leads to premature wear of expensive parts inside the automatic transmission and its failure.