Fuel-efficient refers to vehicles or machines that use less fuel to operate, maximizing energy use and minimizing waste. This efficiency is often measured in miles per gallon (MPG) for cars, indicating how far a vehicle can travel on a specific amount of fuel. Improving fuel efficiency can lead to lower fuel costs and reduced environmental impact, as it decreases greenhouse gas emissions. Many modern vehicles, including hybrids and electric cars, are designed with advanced technologies to enhance their fuel efficiency, making them more sustainable options for transportation in today's world.