Hello, 5w-40 and 0w-40 are both motor oil designations. The letter W stands for winter, and in fact all oils with the letter W are winter and summer oils.

The number 40 represents the high-temperature viscosity grade of the oil. The larger the number, the more viscous the oil is at high temperatures, and the thicker the film thickness equates to, the better the sealing and protection.

The numbers 5 and 10 represent the minimum temperature, or low-temperature fluidity, of the oil. 0 means that the oil's minimum temperature is -35 degrees Celsius, and 5 means that the oil's minimum temperature is -30 degrees Celsius.

If your car's minimum winter temperature is higher than -35 degrees Celsius, then 5w-40 and 0w-40 have the exact same effect on your car.