What is the difference between 15w40 and 10w40?
2 Answers
The main difference between 15w40 and 10w40 engine oils lies in their low-temperature fluidity. Engine oil primarily serves the following functions: 1. It effectively protects internal engine components, reducing wear and preventing aging. 2. Inside the engine, it minimizes mechanical friction resistance, ensuring smoother operation. 3. It helps lower the internal temperature of the engine, aids in heat dissipation, prevents rust and aging of internal parts, and extends the engine's service life.
The difference between oil viscosity grades like 15w40 and 10w40 mainly lies in low-temperature fluidity. The 'W' stands for winter, where 15 indicates normal flow at around -20°C, suitable for warmer regions, while 10 means better flow at around -30°C, allowing quicker starts in cold weather. Both have the same high-temperature viscosity of 40, offering similar protection under high heat. In southern regions, I often choose 15w40 because winters aren’t too cold, ensuring smooth starts and slightly better fuel efficiency. However, in northern areas or during severe cold, 10w40 is definitely superior, as it helps the engine warm up faster, reducing wear. The car manual usually recommends oil based on regional conditions. Using the wrong type may lead to hard starts or short-trip wear, especially for older cars—don’t risk major damage to save a little. In short, adjust based on climate and vehicle age, and it’s best to have a mechanic evaluate during oil changes.
