Issues and responses
Automobiles are developed to satisfy various requirements, including safety, comfort, economy and convenience. Fuel economy, in other words low fuel consumption, is a critically important issue for the automotive industry. There is now a particularly pressing need for even greater fuel economy in order to decrease CO2 emissions so as to prevent further global warming.

Improvements in engine efficiency
A fuel-efficient engine generates motive power using less fuel. To achieve lower fuel consumption, chemical energy in the fuel has to be converted into thermal energy with greater efficiency. The automotive industry is working to improve engine efficiency through the implementation of various technologies including increased compression ratios, variable valve timing, lean-burn engines and in-cylinder direct injection, as well as through the development of lighter engines and the reduction of friction.

Improvements in power train efficiency
Automatic transmissions are commonly used to achieve a safer, more comfortable drive. Improved torque-converter efficiency and lock-up mechanisms preventing slip loss are used to improve fuel efficiency. A greater number of gears makes it possible to set better gear ratios in accordance with driving conditions and to convey engine power more efficiently, thereby contributing to improved fuel efficiency. The CVT (continuously variable transmission) takes this technology even further by improving efficiency through "stepless" gear-shifting.

Reductions in vehicle weight
Reducing body weight contributes greatly to improved fuel economy, but safety must also be taken into consideration. Methods for reducing vehicle weight include the use of light metals and plastics and the more rational design of the vehicle body and parts. For example, high-tension steel sheets are now being used to create thinner, lighter bodies, and lightweight materials such as aluminum for engine blocks and wheels and plastic for bumpers are being employed to a greater extent. Recycling is another factor taken into consideration in the process of vehicle design and development.

Improved aerodynamics
Air resistance places a major load on a moving vehicle. Air resistance is reduced--in other words, aerodynamics are improved--by keeping the number and size of protuberances on the side windows and body to a minimum, by using surfaces which are as flush as possible on the underbody, and through other considerations in the form of the body aimed at making airflow as smooth as possible.

Reductions in rolling resistance
Improvements in tread patterns, tire materials and tire structures are being made to improve fuel economy without hampering steering stability or brake performance.