Highway fuel refers to a type of gasoline that is specifically formulated for use in automobiles and other vehicles designed for driving on highways. It typically has a higher octane rating than regular gasoline, which means it can resist igniting until it reaches a much higher temperature than regular gasoline. This helps prevent pre-ignition or "knocking" that could damage the engine. Highway fuel is also often enhanced with additives to help clean and protect the engine from wear and tear caused by prolonged high-speed driving on highways.