Fuel efficiency refers to the ability of a vehicle or machine to maximize the energy output from the fuel it consumes. The main goal of fuel efficiency research is to develop technologies and solutions that can improve the performance of various engines, vehicles, and equipment while reducing fuel consumption and emissions. This includes optimizing aerodynamics, engine design, drivetrain efficiency, and using alternative fuels or hybrid powertrains. By improving fuel efficiency, researchers aim to reduce environmental impact, decrease operating costs, and enhance energy security. This research area is critical in addressing issues related to climate change, air pollution, and reliance on fossil fuels.