求翻译：教练车使用时如何省油，教练车省油有诀窍：为了节约能源，不少国家制定了限制教练车油耗的法规，从而促进了燃油经济性的不断提高。随着技术的进步，近年来发动机燃油经济性的提高，教练车自重的降低，教练车空气阻力和轮胎阻力的降低，传动效率的提高，都使汽车的经济性有了大幅度的提高。是什么意思？

How coach cars used fuel, coaching tips for car fuel: in order to save energy, many countries have limited coaching of vehicle fuel consumption regulations, so as to promote continual improvement in fuel economy. As technology advances, the improvement of engine fuel economy in recent years, coaches reduced car weight, the coach car and tire resistance reduced air resistance, improving transmission efficiency, make the car's economy has been significantly improved.