1. Viscosity: 5w30 oil is thicker at lower temperatures, providing better engine protection during cold starts and ensuring proper oil circulation. 5w20 oil may be too thin, leading to reduced oil pressure and inadequate lubrication in cold weather.
2. Low-temperature flow: The "w" in 5w30 stands for winter. 5w30 oil has a lower viscosity index and flows better at lower temperatures than 5w20 oil. In extremely cold conditions, 5w20 oil may not flow as well, causing difficulty in starting the engine and potentially leading to damage.
3. Warranty and manufacturer specifications: Using an oil that is not recommended by the manufacturer may void the vehicle's warranty. Subaru likely recommends 5w30 oil for your 1998 model based on various engineering and performance considerations, and deviating from this could potentially cause problems.
4. Engine wear and performance: If 5w20 oil is used for an extended period in northern Minnesota's cold climate, it may not provide sufficient protection for the engine components. This could lead to premature wear and tear and potentially reduced engine performance over time.
It's always best to follow the manufacturer's recommendations for your specific vehicle, considering the climate and driving conditions in your region. If you're unsure about the appropriate motor oil for your 1998 Subaru, consult a trusted mechanic or refer to the vehicle's owner's manual.
