What is the difference between 20w and 15w engine oil?

[LaJuliana]

20w and 15w engine oils differ in the following aspects: 1. Different properties: For the 20w50 specification, the 20 indicates the minimum applicable temperature of the oil is -15 degrees Celsius, while the 15 in 15w-40 indicates the minimum applicable temperature is -10 degrees Celsius. 2. Different viscosity: 20w50 oil is a multi-grade viscosity oil, whereas 15w-40 is not. 3. Different values: The W in the designation stands for Winter, and the preceding number indicates the oil's low-temperature fluidity—the smaller the number, the better the low-temperature fluidity. The number following the W represents the oil's viscosity grade at 100°C—the larger this number, the better the protection the oil provides to the engine at high temperatures.