Are manual transmissions really that much better for the environment?

Illuminating answers to environmental questions.
Oct. 30 2007 7:36 AM

Jesus Would Drive a Stick Shift

Are manual transmissions better for the environment?

Illustration by Robert Neubecker. Click image to expand.

I've read that cars with manual transmissions get 8 percent better gas mileage than their automatic counterparts. I'm certainly no gearhead, but doesn't that mean that manuals are a lot better for the planet? Can I dramatically reduce my carbon footprint (as well as save some cash at the pump) by switching to a stick shift?

Perhaps, though you'll need to be fairly proficient at shifting gears in order to realize noticeable savings. According to the Environmental Protection Agency's fuel economy ratings, cars with manual transmissions typically beat their automatic peers by a mile or two per gallon. This is largely because manuals give you more control over an engine's exertions. Despite recent advances in slushbox design, humans are still better than automated systems at recognizing precisely when to shift gears. And smart shifting enables you to limit an engine's rotations per minute, which translates into less fuel consumption.

But getting the most out of manual requires a stick-shift savvy that's often lacking in American drivers raised on automatics. If you're lazy about shifting and allow your RPMs to soar unnoticed, then you might actually guzzle more gas than if your car were equipped with a well-engineered slushbox. The federal fuel-economy ratings acknowledge as much, by including an important caveat: "Your vehicle's fuel economy will almost certainly vary from EPA's estimate. … It varies significantly based on where you drive, how you drive, and other factors." So, unless you're prepared to be a vigilant, skilled motorist, you're probably not going to save much, if any, fuel by adopting a stick shift.

If you're up for the challenge, though, you can likely beat the EPA's estimates and achieve fuel savings of up to 15 percent. Aside from paying constant attention to RPMs and trying to reach high gears quickly, you should also try shifting into neutral and coasting when safe. And it'll obviously help your cause to follow the basic tenets of hypermiling, which also apply to automatics: Keep your tires properly inflated, avoid stop-and-start traffic, and remove unnecessary weight from your trunk and back seat.

But even if you go stick and drive like a pro, how much will it affect your overall carbon footprint? Let's be optimistic and assume you shave 15 percent off of your annual gas consumption. The Department of Energy estimates that the average American driver uses 500 gallons of gas per year, so we're talking about a reduction of 75 gallons. Since a gallon of gas emits 19.564 pounds of carbon dioxide—yes, folks, really—you'd be reducing your annual CO2 output by approximately two-thirds of a metric ton. For comparison's sake, if the average American cut out flying for a year, he or she would reduce their carbon dioxide emissions by a little under half a metric ton.

This calculation, however, doesn't include some less obvious benefits of manual transmissions. The brake pads on stick-shift cars, for example, tend to wear out less rapidly than those on automatics. And manual transmissions are relatively cheap to fix and replace, so you can wait longer to buy a new vehicle. Manufacturing auto parts is energy-intensive, so anything that can be done to curb their production has to be a plus.

But the Lantern doubts there will ever be a stick-shift revival in the United States, no matter how much gas prices and temperatures soar. Gearheads will always adore manuals, but they're in the minority—most Americans prefer the ease of an automatic, especially on gridlocked freeways. Fewer than 9 percent of new cars in the United States are manuals, and that figure is set to drop to 6 percent by 2012. And rare is the driving school that teaches teenage newbies how to work a clutch.

Is there an environmental quandary that's been keeping you up at night? Send it to ask.the.lantern@gmail.com, and check this space every Tuesday.

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