Good fuel economy is a combination of good vehicle maintenance and sensible driving. Good maintenance entails a properly tuned engine, with a clean air filter, well aligned and balanced front wheels and tyres with the correct air pressure. Sensible driving involves smooth, steady acceleration; driving at moderate speed on the highway; avoiding overloading and excessive use of the air conditioner; and not leaving the engine idling (especially in stop-and-go traffic) rather than turning it off.