Which of the following can improve vehicle emissions efficiency?

Regular maintenance of the vehicle is essential for improving emissions efficiency because it ensures that all engine components, such as the air filter, fuel injectors, and exhaust system, are functioning properly. This maintenance can include tasks like changing the oil, replacing worn-out spark plugs, checking tire pressure, and ensuring that the emissions control systems are working effectively. A well-maintained vehicle runs more efficiently, reduces fuel consumption, and minimizes harmful emissions. By scheduling regular maintenance, drivers can ensure that their vehicle adheres to emissions standards and reduces its environmental impact.

In contrast, using higher grade gasoline may not necessarily translate to better emissions efficiency, as the benefits can vary based on the vehicle's design. Driving at higher speeds generally decreases fuel efficiency and increases emissions, while ignoring warning lights could lead to unresolved issues that negatively affect the vehicle's performance and emission levels. Thus, regular maintenance emerges as the most effective strategy in improving vehicle emissions efficiency.