1972 Chevrolet C-10 Super Cheyenne on 2040-cars

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This map reveals the cleanest vehicles based on location

Naysayers love to point out how dirty the electricity grid mix is when it comes to charging electric vehicles. Curmudgeons are eager to jump into any conversation about EVs to enlighten the lucky listeners about how plug-in cars contribute to pollution, sometimes even throwing in a dash of climate-change denial for good measure. (Thanks, buddy. Pray, tell me more about the plight of oppressed SUV owners.) Unless someone buys an EV just because they think they're cool (which, yeah, they often are), they probably have at least a passable understanding of their environmental pros and cons. As many EV owners are already aware, location has a lot to do with any particular plug-in car's carbon footprint. Still, there's always more to know, and knowledge is not a bad thing, especially if one uses it to do the right thing. That's why this handy-dandy map from Carnegie Mellon University is so interesting. CMU researchers have compiled information about the lifecycle greenhouse gas emissions of various EVs based on where they're charged, as compared to gasoline-powered vehicles. The researchers looked at the Nissan Leaf, Chevrolet Volt, and Prius Plug-In Hybrid versus the gasoline-dependent Toyota Prius hybrid and the stop-start-equipped Mazda3 with i-ELOOP and compared grams of CO2 emitted per mile. CMU takes into account the grid mix, ambient temperature, and driving patterns. CMU takes into account the grid mix based on county, as well as ambient temperature and driving patterns in terms of miles traveled on the highway or in the city. For instance, if you drive a Nissan Leaf in urban areas of California, Texas, or Florida, your carbon footprint is lower than it would be if you were driving a standard Toyota Prius. However, if you charge your Leaf in the Midwest or the South, for the most part, you've got a larger carbon footprint than the Prius. If you live in the rural Midwest, you'd probably even be better off driving a Mazda3. Throughout the country, the Chevrolet Volt has a larger carbon footprint than the Toyota Prius, but a smaller one than the Mazda3 in a lot of urban counties in the US. The Prius and Prius Plug-In are relatively equal across the US. Having trouble keeping it straight? That's not surprising. The comparisons between plug-in and gasoline vehicles are much more nuanced than the loudest voices usually let on.

Watch this week's Top Gear America used-car challenge

Top Gear America is back for the penultimate episode of the first season. Used car challenges were some of the highlights of the original UK edition. In our exclusive clip, Tom Ford, Antron Brown and William Fichtner run their $7,000 sports cars in a drag race. As expected, the trio chose very different cars for the challenge. Watch the video to see if a Subaru WRX's all-wheel drive can overcome a power deficit to beat a Ford Mustang and a Chevy Corvette. Brown and Fichtner also spend some time relaxing with an old Jeep Wagoneer. Like them, we're really hoping Jeep will bring back the Wagoneer nameplate. Brown also drives a Maserati Levante, proving that not all family cars need be boring. This week's guest star is actor, rapper and former host of Pimp My Ride, Xzibit. Top Gear America airs Sundays at 8 p.m. Eastern on BBC America. Related Video: Celebrities TV/Movies Chevrolet Ford Subaru Top Gear exclusive top gear america

2015 Chevrolet Corvette Z06 Convertible is the track car for sun worshippers

Supercharged, 6.2-liter V8? Check. Seven-speed manual? Check. Obsession with weight? Check.
What did you expect when Chevrolet said it was bringing a new Corvette variant to the 2014 New York Auto Show? Maybe a sticker and trim package, like the C6 Corvette Grand Sport or a tie-in deal like the Black Widow car from Chicago? On the opposite end, maybe there was an even more hardcore Z06 waiting in the wings. Who knew?