What Does Idle Speed Mean?
3 Answers
Idle speed refers to an operating condition of a car where the engine runs in neutral gear. The engine speed during idle is called the idle speed, which can be adjusted by modifying the throttle opening size, among other methods. Idle speed means the engine is "producing power without doing work." When the engine is running, if the accelerator pedal is fully released, the engine enters idle mode. When adjusting the idle speed, the RPM should not fluctuate abruptly, as this can cause premature wear to the engine. It is best to have the idle speed adjusted at an automotive repair facility. The idle speed can be adjusted by modifying the throttle opening size or the idle fuel supply. Generally, the optimal idle speed is the lowest RPM at which the engine operates smoothly within the idle range and maintains good acceleration performance.
Idling refers to the state where the car is stationary, but the engine is still running. I drive to work every day and often encounter situations like waiting at red lights or traffic jams where the car isn't moving, but the engine keeps chugging away. In such cases, the RPM stays around 700 to 900, much lower than when driving. Prolonged idling wastes gasoline unnecessarily—about one liter per hour—increasing maintenance costs and emitting harmful gases that pollute the environment. I've calculated that the fuel wasted annually from idling alone could power my car for dozens of kilometers. Modern cars have computer-controlled idling systems; if the RPM is unstable or the engine suddenly stalls, it might be due to a dirty throttle body needing cleaning. To save fuel and protect the environment, many new cars now come equipped with automatic start-stop systems that shut off the engine at red lights and restart it when the light turns green. Developing good habits—like turning off the engine during short waits, using Bluetooth calls instead of parking to chat—can effectively reduce idling time.
Idling refers to the situation where the car is stopped but the engine is still running, such as when waiting for a friend in a parking lot or temporarily pausing by the roadside. As someone who has been driving for many years, I've observed that idling consumes fuel without generating any forward motion, which is purely wasteful. Data shows that idling for one hour consumes approximately 0.8 liters of gasoline, equivalent to driving a small car for several kilometers, while also increasing carbon emissions and worsening air quality. Many people idle their cars to warm them up in winter, believing it protects the engine, but in reality, it harms the vehicle by causing carbon buildup and reducing its lifespan. I recommend avoiding prolonged idling whenever possible, especially for older vehicles. If waiting is unavoidable, limit it to under three minutes. Many cities, like Shanghai, have regulations imposing fines for idling beyond the allowed time, so it's best to develop the habit of turning off the engine. The auto start-stop function is worth using, as it automatically cuts off idling, saving fuel and being environmentally friendly.
