What does 5W-40 mean for car engine oil?
3 Answers
Engine oil "5W-40": The "W" stands for "winter", indicating it's for winter use. The number 5 before "W" represents the viscosity under low-temperature conditions. Below is a relevant introduction about the selection of engine oil grades: 1. German cars: Start with 0W40/5W40, although some 30-grade oils are also suitable for German cars. Small-displacement German cars can use 30-grade oils that meet viscosity requirements when new. 2. Domestic, American, Korean, and French cars: Generally use 0W30/5W30 within 60,000 kilometers, and switch to 0W40/5W40 after 100,000 kilometers. These four types of car engines have relatively consistent characteristics. The grade can be selected according to displacement: small-displacement (below 1.8L) can use 0W30 grade long-term, while large-displacement (above 2.0L) can switch to 0W40 grade earlier.
After driving for so many years, the meaning of 5w-40 engine oil for cars is essentially about the oil's performance in both cold and hot weather. The "5w" indicates good low-temperature fluidity, meaning the engine can start easily even at around -25°C, so you don't have to worry about the car not starting in winter. The "40" represents high-temperature viscosity, ensuring the oil doesn't thin out when driving at high speeds in summer, protecting engine components from wear. My car often uses 5w-40 because it's a multi-grade oil, suitable for all seasons, fuel-efficient, and durable. Choosing the wrong viscosity might lead to slow starts in winter or engine overheating in summer, so I always advise car owners to select oil based on their driving environment. For example, in colder northern regions, it's best to avoid oils with high W values. Additionally, the quality of the oil affects its lifespan, so it's better to use fully synthetic types to reduce carbon buildup.
As a car enthusiast, I really enjoy studying the details of motor oil. The "W" in 5w-40 stands for "Winter," and the number 5 indicates smooth flow in cold weather, reducing engine startup resistance. The 40 represents viscosity retention in high-temperature environments, preventing insufficient lubrication when overheating. This multi-grade design allows the oil to automatically adjust across different temperatures, ensuring smoother engine operation. I've experimented with various oils in my compact car and found that 5w-40 offers strong all-around performance—it doesn't freeze in winter and provides robust protection in summer. The key is to check the oil's API certification to ensure it suits modern engines, preventing rust and oxidation. If you frequently drive long distances, high-temperature protection becomes even more critical—choosing the right oil can extend your engine's lifespan.
