Fuel quality refers to the characteristics of fuel that determine its performance and efficiency in engines. It includes factors such as the fuel's chemical composition, purity, and energy content. High-quality fuels burn more efficiently, produce fewer emissions, and help engines run smoothly, which can lead to better fuel economy and reduced maintenance costs. Various standards and regulations, such as those set by the Environmental Protection Agency (EPA) and American Society for Testing and Materials (ASTM), help ensure fuel quality. These standards address aspects like octane rating for gasoline and cetane number for diesel, ensuring that fuels meet specific performance criteria for different types of engines.