What is the difference between 5w30 and 5w40?

2 Answers
DelCole
07/28/25 9:22pm
The difference between 5w30 and 5w40 lies in their kinematic viscosity standards at 100 degrees Celsius. In simpler terms, 5w40 oil has higher viscosity than 5w30, providing better protection under high-temperature conditions. The main factors for choosing between these oils are as follows: 1. Vehicle type: Different car models require different oils. The choice of oil should follow the car manual. American cars generally have more precise engines, making 5w30 oil (lower viscosity) the most suitable. German cars often have turbocharged engines with larger gaps, requiring 5w40 oil (higher viscosity). 2. Traffic conditions: To minimize the impact of road conditions on oil lifespan, choosing the right oil viscosity is crucial. For daily commuting, a lower viscosity oil (5w30) is recommended to reduce carbon buildup. For frequent highway driving, where engine heat and wear are more severe, 5w40 oil is advised. 3. Vehicle age: This is also a critical factor. As a car ages, engine wear and tear become more significant, necessitating the use of 5w40 oil for better protection. Newer cars can use 5w30 oil.
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DeHenry
08/12/25 2:01am
Having driven a commuter car for over a decade, I've found that the main difference between 5W30 and 5W40 lies in their high-temperature viscosity. Simply put, 5W30 is slightly thinner when the engine runs hot, making it ideal for regular city driving or quick cold starts, with noticeable fuel efficiency advantages. On the other hand, 5W40 is thicker, offering stronger protection during summer highway trips or under heavy loads, reducing engine wear. From the manual, I learned that new cars, especially Japanese models, often use 5W30 for cost and fuel savings, while older vehicles or those in high-temperature regions benefit more from 5W40 for durability. Don’t overlook climate impact—use 40 in southern summers to avoid overheating and 30 in northern winters to save on fuel. Remember, choosing oil depends on your car’s needs; switching randomly can affect lifespan and performance.
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