All my life, I thought there was just one way to get to my hometown’s ShopRite: right on Fair Street, right on Gleneida Avenue, right into the parking lot. That was until I plugged ShopRite into Google Maps. Now I had two options. I could turn right into the parking lot in front of the grocery store or, if I felt compelled, enter closer to Gold’s Gym and cut across the asphalt sea. Either route would take four minutes, the app said, but the latter earned the Google Maps eco-mode seal of approval: a little green leaf. A blurb informed me that I would save 6 percent gas by turning into the lot before, rather than after, the spot where my mom takes Bodypump classes. I could do my part to save the world.

It’s been two years since Google announced its Maps eco-routing feature. For all trips by car in the U.S., Canada, and much of Europe, the app defaults to recommending the most environmentally friendly route, as long as it’s not that much slower than the alternative. If the time difference between routes is negligible, the app defaults to the one that saves gas. The feature’s launch was met with significant internal buzz. Google’s CEO, Sundar Pichai, said that it could save “over one million tons of carbon emissions per year—the equivalent of removing over 200,000 cars from the road.”

That sounds great. But those numbers are less impressive when you consider that the EPA estimated on-road-vehicle emissions of about 1.5 billion tons of CO2 last year, and that nearly 103 million cars were registered in the United States in 2021. The tiny green leaf may help the planet a little, but it might also make things worse by giving drivers like me a false sense of accomplishment as we continue destroying the planet with gas-guzzling personal vehicles. Eco-mode is a little nudge in a time when little nudges just don’t feel like enough—a sign of how much inconvenience any of us is actually willing to suffer in order to mitigate climate change.

The question of how much eco-mode is actually changing drivers’ behavior is difficult to answer. For one thing, the “green” routes that Google recommends are, in many cases, exactly the same routes it would’ve offered anyway. “The fastest route and the most fuel-efficient one are the same the vast majority of the time,” Rosa Wu, a product manager at Google Maps, told me, though the company was unable to provide any precise numbers. In cases where there are multiple options, Wu said, eco-mode does make it easier for drivers to choose a more sustainable route when planning a trip.

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When I talked with David Reichmuth, a senior engineer in the Clean Transportation program at the Union of Concerned Scientists, he asked the app for directions from his Oakland, California, home to his parent’s house in Petaluma, about 45 miles northwest. The result was fantastic: “It says right now that I will save 62 percent gas,” he told me about the 40-minute trip. But the alternative was a roundabout two-hour journey that took him south to San Jose, north through San Francisco, and over the Golden Gate Bridge (and avoided a $7 toll). “So I guess, yes,” he said, “you do save 60 percent over driving the wrong way.”

When eco-mode’s recommendations do differ from the fastest route available, estimating how much gas is saved is not trivial. To calculate its eco routes, Google Maps relies on a vehicle-energy-consumption model co-created by Jacob Holden, a research scientist at the National Renewable Energy Laboratory. Predicting how much gas a certain vehicle will consume at a certain speed on a certain path is a fairly simple engineering problem, Holden told me, but it’s harder to transfer this information when road conditions, and people’s individual driving styles, are unpredictable. “You and I and 1,000 of our friends could drive the same stretch of road, and we’ll all drive it a little bit differently,” he told me. Still, he thinks eco-mode’s predictions are roughly accurate; one paper he co-authored in 2018 found that the NREL’s current methodology “should accurately select the route that consumes the least fuel 90% of the time.”

We also have no way of knowing the net climate impact of eco-mode other than to take Google’s word for it. Konstantinos Katsikopoulos, a behavioral-science professor at the University of Southampton, wanted to see more data on the 200,000-car figure especially. Though a 200-word endnote in Google’s 2023 environmental report outlines how the company reached that figure, it doesn’t include the raw data. “Maybe they’re assuming that nobody’s interested to know more or they couldn’t understand it,” he told me. But to him, it mostly seemed opaque.

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Eco-mode’s impact may be small, at least so far, but wide-scale eco-nudges could cumulatively play a role in reducing overall emissions. A 2022 Intergovernmental Panel on Climate Change (IPCC) report, according to a summary by one of its co-chairs, concluded that “having the right policies, infrastructure and technology in place to enable changes to our lifestyles and behaviour can result in a 40–70% reduction in greenhouse gas emissions by 2050.” Google Maps isn’t helping people buy electric vehicles, retrofit their houses with energy-efficient technologies, or install heat pumps—changes that would undoubtedly carry a much larger benefit—but it’s still a behavior change. If small reminders incorporated into tools people already use in their daily lives could make a real dent in emissions, the world might indeed warm more slowly. And in that sense, eco-mode’s successes are as instructive as its shortcomings.

But that doesn’t mean people will use it when the more sustainable choice is actually slower. Holden told me that, on his own trips, he’ll more often than not take the eco-route, but it’s not always great. “There are certainly times where I’ll be given a route that’s recommended as efficient and we'll just kind of chuckle at the impracticality,” he told me. If the app instructs him to  avoid the highway in favor of a slightly longer drive through a series of stoplights, he’ll believe the recommendation—it’s based on his own model, after all—but still drive the highway route. “And I think that’s really interesting,” he said. “Me of all people, I’m reaching that conclusion.”

To impress the benefits of the eco-routes upon drivers like Holden, Google is considering retooling how its eco-routes are presented, Wu told me. Maps doesn’t display emissions estimates—such as carbon-dioxide equivalent—because they’re confusing for regular drivers, she said. “When we were doing research, we found that users had no conception of emissions.” But the percentages might not be persuasive enough to change people’s behavior. Instead of “saves 2% gas,” the company is thinking of presenting potential financial savings at some point—take this route, spend four more minutes driving, and save $1.45.

Kate Brandt, Google’s chief sustainability officer, told me repeatedly that the goal of programs like eco-mode and Google Flights’ carbon-footprint calculation (which estimates how many kilograms of CO2 I’ll contribute to the atmosphere depending on which flight I pick) is to provide “helpful information that people are seeking.” But as I scrolled through Maps over the past few weeks, I wondered who was seeking some of the information Google offered: the route to upstate New York that would take 40 more minutes and, depending on the time of day, possibly save me 2 percent on emissions; the ShopRite parking-lot maneuver that would save a couple of teaspoons of gas.

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If Google Maps is so intent on showing me the greenest way to get to the grocery store, its eco-friendly nod would perhaps more helpfully be directed toward a non-driving option. Though Google Maps provides helpful walking, biking, public-transit, and mixed-mode directions, no amount of industrious trekking will earn you a green leaf. Reichmuth thinks this is a mistake. When he pulled up routes from his home to San Francisco’s Oracle Park, he wondered why Google bestowed the eco seal of approval on any driving route when he could take public transit, get there in about the same amount of time, and not waste minutes and fuel parking.

Holden, despite his gas-use models, felt similarly. “The actual solution here is to get on your bike and go to Trader Joe’s,” he said. “That will be the most efficient path.”