The Difference Between 5W40 and 10W40 Engine Oil
3 Answers
5W40 and 10W40 engine oils differ in their applicable temperature ranges. Below are the key distinctions: 1. 5W40 indicates the oil's minimum applicable temperature is -30°C, whereas 10W40 signifies a minimum applicable temperature of -25°C. 2. The letter W stands for Winter, meaning oils with W are suitable for both winter and summer use. The number 40 represents the oil's high-temperature viscosity grade – the higher the number, the stronger the oil's high-temperature viscosity and the thicker the oil film. 3. Engine oil, also known as motor lubricant, serves multiple functions including lubrication and wear reduction, auxiliary cooling, sealing and leak prevention, rust and corrosion protection, as well as shock absorption. It is often referred to as the 'blood' of a vehicle.
I remember being torn between 5w40 and 10w40 for my first oil change, but later understood the key difference lies in winter performance. 5w indicates better fluidity at low temperatures, allowing the engine to start quickly even at -25°C and reducing wear; 10w flows slightly slower in the same cold conditions, potentially making startup a bit harder. Both share the same high-temperature rating of 40, offering equal engine protection in summer. The difference impacts fuel efficiency—5w40 performs more efficiently in cold weather, saving some fuel; 10w40 works fine in warmer regions. From my experience, northern car owners should opt for 5w40 to prevent freezing issues, while 10w40 is practical enough in the south. Never skip regular oil quality checks—protecting engine longevity is crucial. Always refer to the engine manual as a reliable guide; avoid random experiments to prevent vehicle damage.
After years of repairing cars, I've encountered many differences in engine oils. Simply put, the difference between 5w40 and 10w40 lies entirely in the first number. 5w has lower viscosity at low temperatures, flows faster during cold starts, and provides quicker lubrication to protect bearing shells; 10w is slightly thicker under the same low temperatures, which may cause a slight delay in startup and potentially increase minor wear. Both have a high-temperature rating of 40, ensuring protection for the chain under high temperatures. I recommend using 5w40 for new cars or turbocharged engines to improve efficiency; for older cars, 10w40 is more cost-effective and suitable. Environmental factors are crucial—stick to 5w40 in cold regions, while 10w40 in warmer areas won’t compromise safety. Oil selection also affects maintenance intervals, and matching it with the vehicle's age ensures peace of mind. Don’t overlook these details; they can extend the engine’s operational lifespan.
