How long is the best time to warm up your car in winter? 30 seconds or 3 minutes? Experienced drivers: This is the best way

As the cold wave hits most cities across the country, many drivers have to face a problem when starting their cars in the morning: warming up the car. Especially for those who park their cars in outdoor parking lots, this is a process that must be experienced. However, this seemingly simple "warming up the car" action is really different for everyone. Some people are used to not adding gas after starting the car, letting the car stand still for a while before driving; others believe that it is better to drive slowly immediately after starting the car... How can you make your beloved car, which has been "neglected" for a whole night, quickly enter the working state from the "ice cellar" and minimize the loss of the engine and various parts? Let's listen to the experts for advice.

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01

"Warming up" is indeed necessary

But no need to overdo

Let me first say the conclusion: "Warming up the car" itself is necessary, but it should be done in accordance with the vehicle manual. Many people have an inaccurate understanding of this " degree ", and even many drivers have the problem of "overheating the car".

Almost all thermal machinery requires a warm-up process before normal operation, so that the machine can transition from a cold state to a normal working state. The so-called "warm-up" is actually a process of allowing the engine oil and transmission oil to fully contact with various parts of the machine to achieve a good lubrication state, thereby reducing wear. In addition, "warm-up" can also allow various systems of the car to reach the optimal operating temperature, improve the car's driving performance and emission performance. Therefore, in principle, "warm-up" is necessary regardless of winter or summer. In winter, the ambient temperature is lower, the viscosity of the lubricating oil increases, and lubrication is more difficult in a cold state. Therefore, "warm-up" in winter is more valued by everyone.

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However, it should be noted that with the iteration of automobile product technology, the main body of the "warm-up" operation has long been transferred from the driver to the car itself. Therefore, in most cases, the driver only needs to start normally and drive smoothly, without "launch start" or stepping on the accelerator as soon as the car starts. The car will automatically adjust its operating status to ensure that it is in the best working condition.

Regarding "warming up the car", there are many statements on the Internet that "when the engine speed drops from 1200 to around 800, it means the vehicle is ready to start." In fact, the reason why the engine reaches 1200 rpm during cold start is because the thermal management system increases the fuel injection volume and increases the speed to preheat the engine in order to make the vehicle reach the best working state.

02

"Warm car" method

It's better to move than to stand still

Since it is necessary to warm up the car, the next question is: how to warm it up? Many people think that warming up the car is "waiting for a few minutes after starting it before refueling it." There are also some opinions on the Internet that suggest that you should let the car idle for a while before refueling it. Which method is right?

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Answer in a responsible manner: follow the car manual. Because engineers and designers who write car manuals must be the ones who know the car's "temperament" best. Questions such as "Does the driver need to warm up the car?" and "How to warm up the car?" must be clearly answered in the manual. For example, the product manual of a certain car has the following description:

As you can see, engineers do not recommend car owners to warm up the car by standing still, but rather hope that the car owners can start and run smoothly to achieve the ideal working state. In fact, most car manuals currently have similar suggestions.

In fact, within 30 seconds after the car starts, the lubricating oil can lubricate all working surfaces, and it is not appropriate to continue to preheat the engine in situ. On the one hand, the load is small when idling in situ, and the heat generated is also small, so the efficiency of engine preheating in this way is low; secondly, idling in situ only preheats the engine, without considering the transmission system, steering system and braking system, and the warm-up is not sufficient; finally, the emission performance of the vehicle is poor when idling in situ, not only does it produce a lot of carbon deposits, but it is also easy to produce more pollutants.

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Most cars nowadays can adjust themselves to warm up when they are cold started. If the owner still warms up the car by idling it for a long time, it is not only wrong in principle, but also wastes resources. In addition, the main difference between a new car and a car that has been driven for many years is the degree of wear and tear on the inside, which makes no difference in whether it needs to be "warmed up".

03

Electric cars and hybrid cars also need to be warmed up

New energy vehicles do not have the engines and gearboxes of traditional fuel vehicles, but they have a new power source, the power battery, and the ambient temperature is one of the dominant factors affecting the performance of the power battery. As shown in Figure 1, in the lower ambient temperature in winter, the side reactions during the charging and discharging of the power battery increase, and the performance will be greatly attenuated, mainly manifested in: low charging and discharging efficiency, reduced battery capacity, and reduced cruising range.

Figure 1: Effect of ambient temperature on battery range

Source: Shen Zuying et al. Experimental study on the influence of ambient temperature on the charging and discharging performance of electric vehicle power batteries under NEDC conditions [A]. Proceedings of the 2020 China Society of Automotive Engineers Annual Conference

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Therefore, when the ambient temperature is low in winter, electric vehicles and hybrid vehicles need to "warm up the car" or "warm up the power battery" more than traditional fuel vehicles. At present, most new energy vehicles are equipped with power battery preheating systems and thermal management systems, so there is no need for drivers to actively "warm up the car", but for a period of time after starting in low temperature conditions, you should try to drive smoothly and avoid stepping on the accelerator.

Author: Chen Xiaokai, Associate Professor and Deputy Director of the National Engineering Laboratory for Electric Vehicles, Beijing Institute of Technology

Review | Li Gang, Vice Dean and Professor of the School of Automotive and Transportation Engineering, Liaoning University of Technology