Transmission oils: classification and characteristics

Трансмиссионные масла – специальный класс machine oils, intended for use in different friction nodes of vehicle transmissions, as well as in various reducers. Motor and transmission oils are produced on a mineral or synthetic basis, and then alloyed with a variety of additives, but the requirements for transmission are higher, since they work at much higher loads and sliding speeds of rubbing surfaces.

One of the most important indicators of such oilsis the ability to create a protective film on the surface of the friction units to prevent mechanical contact between them. In hypoid gears, oils are used that, when reacting chemically with the surfaces of parts, prevent their skipping, have anti-seize properties. During operation, the transmission oils oxidize and become contaminated, so they must be periodically changed. Good oil is considered to be an oil with a low tendency to oxidation. Since different manufacturers use different additives, their products can not be mixed. When replacing the transmission assembly, it must be thoroughly rinsed, if possible with the same fresh oil.

Классифицируют трансмиссионные масла либо по viscosity, or on operational properties. So according to the SAE (Association of Automotive Engineers) they are divided into nine classes - five year olds and four winter ones (with the W index). For each class, the viscosity index is indicated. SAE 70W or SAE 250, for example. For all-season oils, a double index is indicated (SAE 80W-90, etc.).

API (American Petroleum Institute) dividesoils for 6 classes, depending on the operational properties - GL-1 ... GL-6. These classes are similar to those used in the Soviet GOST 17479.2-85 TM1 ... TM6. The fifth and sixth groups are used for hypoid gears and have the highest lubricity and extreme pressure characteristics.

When choosing gear oils,focus primarily on the conditions of their work. If the class is lower than necessary, the mechanism simply fails, and a higher class of oil has a higher cost, which will lead to cost overruns. It is also important to take into account at what temperatures the transmission will work, and based on this, select a lubricant. SAE 85W, for example, will work at temperatures up to -12 ° С, and 85W already up to -40 ° С. In automatic transmissions, a special low-viscosity fluid is used, so neither engine oil nor gear oil is used there.

Today the market has a large range of manufacturersoffer their gear oils - Lukoil, Total, Texaco, Rexol, Norse and many others. The variety of additives used determines both the quality level of oils and their price range. Mineral, usually, is cheaper, but serves less, synthetics is exactly the opposite. A good compromise in this case would be semi-synthetics, as the golden mean between the first two. You should also beware of fakes and do not buy oil in unchecked stores. Changing a box is always more expensive than taking a good, high-quality oil, especially since they now take care of 60,000 or more kilometers from replacement to replacement.