The W on the oil drum represents multi-level TH degree oil, which is the oil that can be used in winter. When selecting oil, the smaller the number in front of W, the better; the larger the number behind W, the better. Of course, we must also consider the price and applicability. The number in front of W can be subtracted by 35, and the resulting number represents the temperature suitable for winter. For example, 10W-40, with 10 minus 35 equals -25, indicating that it is suitable for use in environments below 25 degrees Celsius, and it will not flow normally if it is cold. The number in front of W is 0, which is suitable for lower temperatures, but at a higher price.
The number behind W represents the high temperature of the private, and can be selected according to the local temperature. For example, if the temperature is up to 30 degrees, choose 30 or 40 degrees and choose 40°. The higher the number, the better the engine protection. Of course, the relative price is higher. Engine oil can deteriorate after a period of use, or it can deteriorate even if it is not used. As the engine oil removes dirt and oil from the engine, it gets dirty and then turns black. Unscheduled oil change will produce a lot of carbon deposits, making the engine difficult to start, difficult to accelerate, even pulling the cylinder to hold the shaft, biting the early damage, overhauling or scrapping in advance.