Skills of selecting engine oil at high temperature in summer
In summer, the car's power becomes weaker. It's not only related to the air conditioner, but also the oil. First, the weather is hot in summer, the temperature is very high, and there are often rainstorms in some places, and the humidity is also very high. This will cause the oil pressure to be too low. Second, some of my friends didn't choose the right engine oil at all. When it comes to high temperature season, the performance of the engine oil is not so good, and the power of the car becomes weaker.
If you compare a car to a human body. Then the engine is equivalent to human's "heart", and the oil is equivalent to human's "blood". When the engine works, it will reach the high temperature of 400 ℃ ~ 600 ℃ due to high-speed friction, so the oil that can be competent for this kind of working environment should at least play the functions of lubrication, antifriction and cooling.
Engine oil is generally composed of base oil and additives. Base oil should meet the above-mentioned functions, while other additional characteristics, such as cleanliness, oxidation resistance, rust resistance, viscosity index improvement, need additives to increase.
What are the criteria for selecting engine oil? As mentioned above, lubrication and antifriction is the most basic function of engine oil. Otherwise, it is more convenient to add water directly. One of the indexes of lubricating degree of engine oil is "viscosity index". Viscosity is well understood, such as honey and water
Honey is more viscous than water. The viscosity of the engine oil is low, and the oil film with enough thickness can not be formed at the place where the engine oil flows, so the lubricating effect is lost; If the viscosity is too high, the parts can't rotate at all in the engine oil, the resistance will increase, and the power consumption will be more.
The viscosity index is a ratio, which is used to measure whether the oil is greatly affected by the temperature. The higher the viscosity index is, the more stable the viscosity of engine oil is at high or low temperature. Different engine oils have different viscosity indexes and can adapt to different environments. What's the meaning of the mark on the engine oil? The viscosity index is mainly classified according to the SAE standard,
The number B after w stands for high temperature performance: the larger the number, the better the viscosity of engine oil at high temperature. The number a in front of W stands for low temperature performance: the smaller the number, the better the fluidity at low temperature and the lower the applicable minimum temperature,
In high temperature viscosity test, 0W engine oil can start normally at - 35 ℃, and the minimum temperature of 5W engine oil is - 30 ℃. The minimum operating temperature of the engine oil is - 35 ℃ plus W,