Is It More Fuel-Efficient to Turn Off the Engine or Keep It Running at Red Lights?

[Edith]

Turning off the engine saves fuel if the red light lasts more than two minutes, while keeping it running is more fuel-efficient if the wait is less than one minute. There is no need to turn off the engine for stops under one minute: The engine consumes a significant amount of fuel during each startup, with a momentary voltage spike that requires more energy than normal operation. If the stop lasts over two minutes, turning off the engine can save some fuel, as the savings outweigh the fuel consumed during restart. However, for stops under one minute, turning off the engine is unnecessary, as the fuel consumed during startup is nearly the same as idling. Disadvantages of frequently turning off and restarting the engine in short intervals: The fuel consumed during startup is greater than that consumed by idling for one minute. The electricity used for one startup typically takes 10 to 20 minutes of driving to replenish. Frequent startups also pose a greater risk of battery drain, leading to potential discharge issues.

[CollinAnn]

Hey, I've actually thought about this question. From a technical perspective, whether turning off the engine at a red light saves fuel depends on the duration of the stop. The engine still consumes fuel while idling, burning about 0.03 liters every 30 seconds, whereas a single start only uses a bit of the starter's electricity, equivalent to 0.02 liters of fuel. So, if the red light is long, exceeding 15 seconds, turning off and restarting the engine can indeed save some fuel. For shorter stops, it's not worth the effort because fuel consumption spikes during startup. Another issue is that frequent starts may affect battery life, especially in older cars, which are more prone to damage. The balancing point suggestion: Try turning off the engine during long red lights in urban areas—it can reduce fuel consumption by 5%-10%, simple and practical.

[LylaLynn]

I usually drive to save money, and I find that turning off the engine at long red lights is more cost-effective. Idling for one minute consumes about 0.025 liters of fuel, which translates to a few cents, but over a year, it can save a few hundred dollars. Don't bother with short stops, as the instantaneous fuel consumption during startup is higher. I've recorded it myself: turning off the engine for red lights longer than 20 seconds shows noticeable savings. For example, during rush hours with multiple red lights, this strategy can save half a tank of fuel per month. Once it becomes a habit, it's simple—just glance at the timer and turn off the engine if the wait is long. Of course, savings are greater in warm weather, and idling a cold engine can also help warm it up a bit.

[Rogers]

As an environmental advocate, I promote prolonged engine shutdown at traffic lights to save fuel. Idling burns fuel wastefully and pollutes the air with carbon and harmful emissions. Shutting off the engine stops everything, especially in congested areas where frequent practice can reduce carbon emissions. Data shows that shutting off for over 10 seconds each time saves fuel and reduces pollution by an average of 10%. I always check the time while driving and take action when estimating a stop of over 30 seconds. Though a small gesture, these accumulated efforts significantly protect the environment. Nowadays, urban air quality improvement relies on such details.

[LeRafael]

Having driven for twenty years, I understand whether turning off the engine at traffic lights saves fuel: it's worth it for long red lights, but troublesome for short ones. Idling consumes little fuel, but it adds up over long stops; starting the engine uses more fuel, and frequent starts wear out the starter. My experience is to turn off the engine if the red light lasts more than half a minute, especially in summer for savings; in winter, idling can warm up the car. Judge based on the traffic light timer, don't be rigid. Saving a bit of fuel daily isn't hard, but safety comes first—only do it when fully stopped.

[AlanaAnn]

Modern car designs now feature automatic start-stop systems that intelligently shut off the engine at red lights to save fuel. As an automotive enthusiast, I've learned these systems average 8-10% fuel savings, with restart consumption being lower than idling losses. Contemporary starters are durable with minimal wear impact. For vehicles without this function, manual operation becomes worthwhile at prolonged stops (e.g., 40+ seconds). Urban driving's frequent stops make habit formation crucial – consistent use can yield substantial annual fuel cost reductions. I recommend practical testing and experiential feedback.