冬季启动拖拉机前，机手会先用启动摇把，摇转发动机曲轴十几圈后再行启动；而在其他季节特别是夏季则不按此法操作。原来，机手们认为冬季气温低，机油黏度大，不容易润滑各零部件摩擦表面；夏季气温高，机油黏度小，容易到达各摩擦面，因此启动前没必要再摇转曲轴了。殊不知 Before the start of the tractor in winter, the driver will start with the crank handle, cranking the engine crankshaft dozens of laps and then start; in other seasons, especially in the summer do not operate this method. It turned out that the hands of those who think the winter temperature is low, the oil viscosity, not easy to lubricate parts friction surface; summer high temperature, oil viscosity is small, easy to reach the friction surface, so there is no need before cranking crankshaft. As everyone knows