Does Turning Off the Engine at Red Lights Save Fuel?
4 Answers
Turning off the engine at red lights does not save fuel. Here are the drawbacks of turning off the engine at red lights: 1. The fuel consumption during ignition is higher than that of idling for one minute. 2. The electricity consumed by one ignition takes 10 to 20 minutes of engine operation to replenish. Here is additional information on why a car might suddenly stall when idling in neutral at a red light: 1. Poor fuel flow at low idle speeds can cause the car to stall, often due to inadequate maintenance. 2. Issues with the car's electrical or fuel systems. Here is additional information on gear selection for automatic transmission cars at red lights: 1. For waits under 20 seconds, use D gear with the foot brake. 2. For waits over 30 seconds in heavy traffic, use N gear with the handbrake. 3. For waits over 2 minutes, use N gear with the handbrake and then turn off the engine.
As a seasoned driver with over a decade of experience, I've experimented with various fuel-saving techniques. The idea of turning off the engine at red lights depends on the duration: shutting it off for less than 20 seconds actually consumes more fuel, as the fuel injected during restart equals about seven to eight seconds of idling. I once timed it and found that turning off the engine only saves fuel if the red light lasts more than 30 seconds. However, for cars with auto start-stop systems, never manually turn off the engine—the system calculates more precisely than you can, and frequent starts can damage the battery. Replacing a battery costs as much as two tanks of fuel. If you're driving a manual transmission in the city, it's even more pointless—repairing a starter motor is painfully expensive.
A friend who drives a hybrid shared a little-known fact with me: turning off a gasoline car at a red light might do more harm than good. Modern direct-injection engines use about 30% less fuel during startup compared to older models, but frequent starts and stops can accelerate spark plug carbon buildup. I’ve developed a habit of checking the traffic light countdown—I only turn off the engine if there’s more than 60 seconds left. If you’re stopped at a red light while going downhill, don’t turn off the engine; keeping it in gear can also save your brake pads. However, automatic transmission drivers should be cautious—restarting requires pressing the brake and shifting to P, which can be hectic and even dangerous. And don’t turn off the engine randomly in rainy weather—the windshield wipers stopping will immediately obscure your view.
I used to believe in turning off the engine at red lights to save fuel, but later test data revealed the truth. The moment a cold engine starts, fuel consumption spikes to 2 liters per hour, much higher than the idle rate of 0.8 liters. Automatic start-stop technology is actually quite smart—it assesses coolant temperature and battery level before deciding to shut off the engine. Last month, my car's real-world test showed that stopping for 60 seconds saves 0.01 liters of fuel, but shutting off for less than 15 seconds increases consumption by 3%. The most cost-effective method is anticipating red lights early, releasing the throttle to coast—this can save enough for half a cup of milk tea.
