What is the difference between 0W-40 and 5W-40 engine oil?

[MacJulianna]

The only difference lies in their low-temperature resistance: The 5W in 5W-40 oil indicates an external low-temperature resistance of -30°C, while the 0W in 0W-40 oil represents an external low-temperature resistance of -35°C. Below are detailed explanations about automotive engine oil: 1. Overview: Engine oil, also known as engine lubricant (Engine-oil), has a density of approximately 0.91×10³ (kg/m³). It serves functions such as lubrication and wear reduction, auxiliary cooling, sealing and leakage prevention, rust and corrosion protection, as well as shock absorption. 2. Composition: Engine oil consists of two main components—base oil and additives. The base oil is the primary constituent of lubricants, determining their fundamental properties. Additives compensate for and enhance the performance shortcomings of the base oil, imparting new characteristics, making them a crucial component of lubricants.

[JosiahRose]

The difference between 0W-40 and 5W-40 motor oil mainly lies in their low-temperature viscosity. The former, like 0W, is thinner at sub-zero temperatures, allowing faster flow when starting the engine and reducing cold-start wear, making it especially suitable for frigid zones or short winter drives. The latter, 5W, is slightly thicker at the same low temperatures, resulting in a slower start, but is more suitable for moderate climates. Both have the same high-temperature viscosity of 40, offering similar protection during high-speed summer driving. When I used them, I noticed that 0W-40 slightly improves fuel efficiency and makes the engine sound smoother, though it might cost a bit more. The choice depends on climate and driving habits: choose 0W for extreme cold and 5W for stable temperatures, but don’t overlook the oil change interval. This affects engine lifespan and driving safety, so regular oil level checks and brand certifications are crucial.

[VanEva]

The core difference lies in their performance at low temperatures. 0W-40 flows better below freezing, making cold starts easier in sub-zero environments, protecting piston bearings, and reducing starter load. 5W-40 has slightly higher viscosity in the cold, making it more suitable for regions near freezing; daily driving differences are minimal. Having used both, I found 0W-40 starts more smoothly in high-altitude mountainous areas, with possibly slight fuel savings. High-temperature performance is identical, as the 40-grade viscosity ensures adequate protection under heat. Regular drivers should choose based on their local climate: prioritize 0W for cold regions, while 5W is cost-effective for temperate zones. Don’t rely solely on viscosity for fuel savings—proper oil change intervals matter more. Adjust based on driving habits, such as opting for 0W for frequent short trips to extend component lifespan.

[MacSawyer]

The difference lies in low-temperature fluidity. 0W-40 is thinner in extreme cold, enabling faster starts and reduced wear, especially beneficial for new cars or frequent start scenarios. 5W-40 is slightly thicker at low temperatures with better cost-performance. Both offer similar high-temperature protection. Having used several motor oils, the fuel consumption difference between these two is less than 0.5L per 100km. Oil selection should consider season and environment: 0W is preferable for northern winters, while switching to 5W in summer saves money. Don't focus solely on viscosity - regular maintenance prevents engine carbon buildup.