Your vehicle’s engine is built and tuned to run on a specific grade of oil. If you put in 5W-30 oil instead of 5W-20 when the latter is the grade suggested by your vehicle’s manufacturer, damage to internal engine parts can occur. Additionally, your engine may experience performance issues such as diminished fuel economy and horsepower.
An oil rating, such as 5W-20 and 5W-30, indicates the viscosity of the motor oil. The viscosity rating is determined by the resistance to flow the oil exhibits under a given temperature. Higher viscosity ratings indicate a thicker oil, which therefore flows less easily. Low-viscosity oils are used in certain engines to minimize oil flow resistance and to maximize performance in cold weather conditions, while high-viscosity oils provide increased protection to engine internals, especially under high temperatures.