In a letter to the hosts of “Car Talk,” a reader shared her experience of taking frequent 150-mile round trips with her boyfriend in her Toyota Yaris. She mentioned that her boyfriend had a habit of turning off the car at every stoplight, which annoyed other drivers and seemed to decrease fuel efficiency. The reader sought advice on whether this strategy was truly beneficial.

According to Tom, the decrease in gas mileage was likely due to the boyfriend’s driving habits. He suggested that the boyfriend’s tendency to accelerate aggressively and drive at higher speeds outweighed any potential fuel savings from shutting down the engine at stoplights.

Ray chimed in, pointing out that modern vehicles equipped with automatic stop/start technology are designed to handle frequent starts. However, he cautioned that continuously turning off the engine at every stoplight could eventually result in expensive repairs, which these vehicles are specifically built to avoid.

He further explained that stop/start technology can increase fuel economy by approximately five percent, depending on the amount of stop-and-go driving involved. However, it’s important to note that cars equipped with this technology have heavy-duty starters capable of handling numerous starts each day, unlike the starters in a Toyota Yaris, which are typically designed for only a few starts at a time.

Ray recommended a more selective approach, advising the couple to turn off the engine only when they anticipate being stationary for two minutes or longer, rather than shutting it off at every brief stop.