What is the difference between fully synthetic 0w40 and 5w40?

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The difference between 0W40 and 5W40 engine oil lies in their low-temperature fluidity. Due to this, 0W40 performs better than 5W40, offering superior cold resistance. Here are some additional details: 1. The meaning of the number before W: W stands for Winter in English, indicating that this oil is suitable for winter use. The presence of numbers after W means the oil is suitable for both winter and summer. The number before W represents the lowest temperature the oil can withstand. A smaller number indicates lower low-temperature viscosity, better low-temperature fluidity, and suitability for lower minimum temperatures, making it easier to start the engine in cold conditions. 2. The meaning of the number after W: The number after W represents the oil's viscosity at 100°C. A higher number means higher viscosity, which allows the oil to form a better protective film at high engine temperatures and makes it suitable for a wider range of temperatures.