What does 0w40 engine oil mean?
2 Answers
Engine oil 0w40 refers to the oil specification. The 'w' stands for winter use, corresponding to a freezing point of minus 35 degrees Celsius. The number 40 indicates that the oil's kinematic viscosity at 100 degrees Celsius is between 12.5mm2s and 16.3mm2s. A smaller number before the 'w' means better engine protection during cold starts, while a larger number after the 'w' indicates higher viscosity. Engine oil, also known as motor lubricant, serves multiple functions including lubrication, wear reduction, auxiliary cooling, sealing, rust prevention, and shock absorption. It consists of base oil and additives. The base oil is the primary component, determining the fundamental properties of the lubricant, while additives enhance and compensate for any deficiencies in the base oil, providing additional performance characteristics.
0W40 actually refers to the viscosity grade of engine oil, like a performance label for the oil. A veteran driver with twenty years of experience will tell you there's a lot of science behind it. The 0 before the W indicates low-temperature fluidity—the smaller the number, the better it resists freezing. 0W means the oil can still flow smoothly like honey to lubricate the engine even in -35°C weather, making winter starts particularly smooth. The 40 after the W refers to high-temperature viscosity, meaning the oil maintains a medium-thick consistency when the engine heats up to 100°C, forming a protective film around high-speed engine components. Northern car owners love this all-rounder—it works from Harbin's icy winters to Hainan's scorching summers. However, whether to choose it or not ultimately depends on your car's manual requirements, especially since older German cars are particularly fond of this grade.
