What is the difference between 10w-40 and 10w-50 engine oil?
2 Answers
The differences between 10w-40 and 10w-50 engine oil are as follows: 1. Different viscosity: Compared with 10w40, 10w50 has higher oil viscosity and better sealing performance, but the engine will consume more fuel. At idle, higher oil viscosity results in lower noise, while at driving speed, higher viscosity oil produces higher noise. Lower viscosity oil has the characteristic of fuel economy. 2. Viscosity introduction: Generally, cars with naturally aspirated engines can use 30 viscosity oil, while cars with turbocharged engines can use 40 viscosity oil. For high-performance, large-displacement engines, 50 or 60 viscosity oil is required. When choosing engine oil, it is essential to select the appropriate viscosity based on the technical characteristics of your car's engine; otherwise, it may affect the engine's performance.
Both engine oils have '10W' on their packaging, looking quite similar, but the key difference lies in the last two numbers: 40 and 50, which indicate their viscosity performance at high temperatures. Simply put, 50 is significantly thicker than 40, especially when the engine heats up during operation. For example, during long summer drives or mountain climbs, the higher viscosity of 50 can maintain more oil film in scorching conditions, offering better protection—particularly useful for older cars or vehicles in sun-exposed regions. However, 40 isn't a bad choice either; it flows more smoothly at normal engine operating temperatures, making urban driving more responsive and slightly more fuel-efficient. If your car's manual recommends 40, don't arbitrarily switch to 50, and vice versa. Don't just chase the novelty of oil grades—match them to your climate and vehicle condition.
