What is the difference between 5W30 and 10W40 motor oil?

[BraxtonRose]

The W in the motor oil grade stands for Winter. The number before W indicates the oil's low-temperature fluidity. The smaller the number, the better the low-temperature fluidity of the oil, making cold starts easier. The number after W represents the oil's high-temperature viscosity. The larger the number, the better the protection performance at high temperatures. The main differences between 5W30 and 10W40 motor oils are as follows: 1. Different applicable temperatures: 5W oil has a freezing point temperature of -30°C, while 10W oil has a freezing point temperature of -20°C. 5W30 oil has better cold resistance than 10W40, can be used at lower temperatures, and has better cold start performance. 2. Different oil viscosity: 30 and 40 indicate the high-temperature viscosity of the oil. 10W40 oil has higher viscosity than 5W30, providing better high-temperature protection and sealing performance. However, higher viscosity does not always mean better performance. Excessive viscosity can increase engine operating resistance, leading to insufficient engine power and increased fuel consumption.