A statistic of automatic transmission maintenance shows that more than 90% of the wear of engine components is caused within 3 minutes after cold start. The main reasons for the need for hot cars are as follows.

1.发动机刚刚启动时，供油系统温度尚低，无法达到工作温度(90~100摄氏度)，汽油不能全雾化，这时的汽油还处于液态，如果强行加速行驶，因为油气混合比过高，会令油耗升高、动力不足，而且汽油燃烧也不好。

1. When the engine is just started, the temperature of the oil supply system is still low and cannot reach the working temperature (90 ~ 100 ℃), and the gasoline cannot be fully atomized. At this time, the gasoline is still in liquid state. If you forcibly accelerate the driving, because the fuel air mixing ratio is too high, the fuel consumption will increase, the power will be insufficient, and the gasoline combustion will be poor.

2.变速箱中的润滑油此时也都因重力作用，囤积在下方，这时如果把车开不够造成的。只有行车时让变速箱齿轮运转起来，才能将所以根本达不到润底部润滑油带起，润滑上部。如果只在原地用怠速热车，由于变速箱没有油泵，所以根本达不到润滑作用。

2. The lubricating oil in the gearbox is also stored under the action of gravity. At this time, it will be caused if the car is not driven enough. Only when the transmission gear is operated during driving can the lubricating oil at the bottom which can not be lubricated at all be brought up to lubricate the upper part. If you only use idle speed to warm up the car in place, the lubrication effect can not be achieved because there is no oil pump in the transmission.

3.车辆在经过长时间停放后，发动机内的机油会集中在下方油底壳内，各部件表面的润滑油膜基本上已经消失，这时启动发动机，其上半部分是没有机油的，需要大约30秒的时间，机油泵才能将机油输送到发动机活塞、连杆和曲轴等需要润滑的部件。

3. After the vehicle is parked for a long time, the oil in the engine will be concentrated in the lower oil pan, and the lubricating oil film on the surface of each component has basically disappeared. At this time, when the engine is started, the upper part of the engine is free of oil, and it takes about 30 seconds for the oil pump to deliver the oil to the engine piston, connecting rod, crankshaft and other components that need lubrication.

现在的汽车一般都使用电子喷油嘴，不同于老式的化油器车型，电喷车供油系统由ECU控制，不受空气流速和温度的影响，燃油雾化程度高，发动机启动后很短时间内就可以达到稳定的怠速。所以热车无需时间太长，只要机油压力升高，水温达到50摄氏度左右就可以了。一般在车发动后等半分钟到一分钟就能让发动机的机油达到各个部件表面。

Today's cars generally use electronic fuel injection nozzles. Different from the old carburetor models, the fuel supply system of EFI vehicles is controlled by ECU, which is not affected by air flow rate and temperature. The degree of fuel atomization is high, and the stable idle speed can be achieved in a short time after the engine is started. So it doesn't take too long to warm up the car. As long as the oil pressure rises and the water temperature reaches about 50 degrees Celsius. Generally, the engine oil can reach the surface of each component after waiting for half a minute to one minute after the car starts.

需要注意的是，除了需要时间让机油覆盖的零件之外，发动机在持续工作之前还需要达到定的工作温度。一般发动机从环境温度达到工作温度需要7到8分钟,但这个过程无需待在原地，只要不以高速行驶就可以。发动机长时间怠速会增加油耗和积炭，不利于。

It should be noted that in addition to the parts that need time to be covered with oil, the engine also needs to reach a fixed operating temperature before continuous operation. Generally, it takes 7 to 8 minutes for the engine to reach the operating temperature from the ambient temperature, but this process does not need to stay in place, as long as it does not drive at high speed. Idling the engine for a long time will increase fuel consumption and carbon deposition, which is not conducive to environmental protection.

综上所述，自动变速箱维修告诉我们热车是比较重要的，所以在这里提示大家，做好相关的注意事项。

To sum up, the maintenance of automatic transmission tells us that hot car is more important, so here we remind you to do a good job of relevant precautions.