Is it problematic to add 0w40 oil to a car that requires 0w20?

[StAmy]

It is highly unsuitable. Although these two types of engine oil have similar low-temperature fluidity, their high-temperature kinematic viscosity differs significantly. Below is a comparison between 0w20 and 0w40: 1. Different viscosity: 0w20 oil has thinner viscosity, resulting in lower fuel consumption; 0w40 oil has higher viscosity, leading to higher fuel consumption. 2. Different fuel consumption: 0w20 can operate at a minimum of -35 degrees Celsius, while 5 can go down to -30 degrees Celsius. Oils starting with 0 perform better in cold winter starts compared to those starting with 5. 0w20 oil offers better fuel efficiency and superior cold-start performance in winter than 0w40. 3. Different vehicle compatibility: 0W20 is purely a winter oil, whereas 0W40 is suitable for most northern regions. Moreover, vehicles that use 0W20 are mostly Japanese and Korean models, which are factory-filled with 0W20 oil. On the other hand, 0W40 oil is more widely available in the market and is commonly used in most Volkswagen models.