Should a 10-Year-Old Car Use 30 or 40 Oil?

[WalterMarie]

For a 10-year-old car, it is recommended to use 40 oil. Due to the significant wear on components such as the valve train and crankshaft connecting rod mechanism in older engines, opting for higher viscosity 40 oil helps form a thicker oil film on the parts. This reduces further wear and noise caused by increased gaps between components. Below are factors to consider when selecting oil viscosity: 1. Vehicle Type: Japanese/Korean and American cars typically use 30 viscosity oil (e.g., 0W-30/5W-30); German cars are recommended to use 40 viscosity oil (e.g., 0W-40/5W-40). 2. Load Conditions: High-load, low-speed vehicles generally require higher viscosity lubricants, while light-load, high-speed vehicles benefit from lower viscosity lubricants. 3. Engine Wear: For cars with over 100,000 km mileage, adjusting oil viscosity is necessary due to increased component gaps from wear, requiring higher viscosity oil for better protective film formation. 4. Local Temperature: In northern winters, oils with better low-temperature fluidity, such as 0W/5W, ensure smooth cold starts.