Which has higher viscosity between 0w40 and 5w40?
3 Answers
0w40 and 5w40 have the same viscosity. Both 5w-40 and 0w-40 are engine oil grades, where the letter W stands for Winter; the number 40 represents the high-temperature viscosity grade of the oil—the larger the number, the stronger the high-temperature viscosity of the oil. The numbers 5 and 0 indicate the minimum applicable temperature of the oil, or its low-temperature fluidity. 0 means the oil's minimum applicable temperature is -35 degrees Celsius, while 5 means it's -30 degrees Celsius. Below are the functions of engine oil: 1. Friction reduction: A sufficiently thick oil film separates the surfaces of relatively sliding parts, thereby reducing wear. 2. Sealing: Engine oil can form a seal between the piston rings and pistons, reducing gas leakage and preventing external contaminants from entering. 3. Rust prevention: Lubricating oil adheres to part surfaces, preventing contact with water, air, acidic substances, and harmful gases. 4. Cushioning: When the pressure in the engine cylinder rises sharply, suddenly increasing the load on the pistons, piston rings, connecting rods, and crankshaft bearings, this load is transmitted and lubricated through the bearings, cushioning the impact load. 5. Cleaning: Good engine oil can carry carbon deposits, sludge, and worn metal particles from engine parts back to the oil pan through circulation, washing away dirt generated on the working surfaces of parts as the oil flows.
Speaking of oil viscosity, let me share from a practical driving perspective. Both 0w40 and 5w40 are commonly used motor oils, but their viscosity levels depend on temperature. Under normal warm driving conditions, such as when the engine reaches 80 to 100 degrees Celsius after running, both oils have essentially the same viscosity—both are grade 40, so there’s no real difference, and both protect the engine well. However, the difference becomes significant during cold starts, especially in winter or early mornings. The '0' in 0w40 means it’s thinner and flows faster, making for smoother starts. The '5' in 5w40 makes it slightly thicker during cold starts, giving it a higher viscosity feel, which can sometimes make ignition harder, especially noticeable in older cars. My advice is to choose oil based on the climate: 0w40 for colder northern regions and 5w40 for warmer southern areas—it saves fuel and protects the engine. Also, don’t just focus on the numbers; oil quality matters too, and don’t stretch oil change intervals too long, as it can affect performance.
As someone who has been driving for years and frequently changes engine oil, I've had experience with both 0W40 and 5W40. Both have a high-temperature viscosity rating of 40, so they perform similarly in terms of viscosity during normal driving, providing smooth engine operation and strong protection. However, at low temperatures, 5W40 has higher viscosity because the '5' indicates weaker fluidity in cold weather. For example, during startup in sub-zero conditions, the engine sound may be slightly heavier. On the other hand, the '0' in 0W40 ensures smoother cold starts with significantly lower viscosity, making it particularly suitable for newer cars. Having used both, I recommend 0W40 in regions with large temperature variations—it saves time and fuel. Viscosity affects driving feel; while there's little difference in summer, it's crucial to choose the right oil in winter to prevent engine wear. Remember to check your oil regularly, avoid mixing different brands, and keep it clean.
