The increasingly stricter environmental regulations and standards aim to reduce the ecological impact of vehicles and promote the sustainable use of natural resources. Improving the energy efficiency of vehicles has become a priority in recent decades. This is a key issue for vehicle development, production, and operation. Several studies and measurements have been conducted to accurately determine vehicles’ energy consumption. This research has investigated and categorized the factors according to external impacts, losses due to vehicle properties, and the effects of vehicle control and energy reduction methods. A better understanding of these factors is crucial for improving energy efficiency.