NEW YORK (MainStreet) — Super-fast sports cars and big brawny pickup trucks are great for some drivers, but here's a look at five environmentally unfriendly 2014 models you definitely don't want to take to a Greenpeace convention.

"If you're going [to buy] one of these cars, 'green-ness' isn't really your priority," says Shruti Vaidyanathan of the American Council for an Energy-Efficient Economy, which recently released its 17th annual Greenest Vehicles and Meanest Vehicles lists.

The rankings highlight 2014 vehicles that the Washington, D.C., think tank considers the most and least friendly to the environment.

Hybrid and electric cars dominate this year's green-autos list, but sportsters, large trucks and big sport utility vehicles account for models the ACEEE sees as least eco-friendly.

"The 'meanest' list is typically ... made up of European sports cars that have ginormous engines and a lot of power behind them, [or] large trucks where weight and poor fuel economy are the contributing factors," Vaidyanathan says.

Her group hopes consumers who want such vehicles (or need them for work) will at least skip the "meanest" models in favor of something somewhat greener.

Look below for a rundown of the models that top of this year's meanest-car list.

All miles-per-gallon figures reflect automakers' published U.S. Environmental Protection Agency estimates, while all dollar figures refer to manufacturers' suggested retail prices for each model's base 2014 edition (including destination charges but excluding any federal "gas-guzzler" tax).

Vehicle weights refer to "equivalent test weights," the weight of a fully loaded vehicle plus 300 pounds to reflect occupants. Pollution ratings refer to how well a vehicle complies with federal and/or California emissions standards. (The Golden State has its own stringent emissions rules that many automakers follow.)

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Fifth-meanest 2014 for the environment: Mercedes Benz G63 AMG
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It's little surprise that a big Mercedes-Benz sport utility vehicle would rate low for eco-friendliness, but the boxy G63 AMG scores particularly badly on the ACEEE's rankings.

Its non-aerodynamic shape, heavy test weight and 536-horsepower V-8 engine combine to produce just 12 mpg/city and 14 mpg/highway. At the same time, the G63 AMG only complies with California's second-loosest emissions standard and the U.S. Environmental Protection Agency's "Bin 5" benchmark. (The EPA ranks models' pollution output in one of 10 "bins," with Bin 1 the greenest and Bin 10 the worst.)

"The G63 AMG is a 6,000-pound vehicle, its fuel economy isn't great and it's certified to one of the dirtier [pollution standards] out there," Vaidyanathan says. "All of that means it's not going to perform well [in terms of eco-friendliness]."

Also see: What Drivers Are Buying in Our Richest Neighborhoods>>

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Fourth-meanest 2014 for the environment: Bentley Mulsanne
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Britain's Bentley Motors will add a built-in champagne cooler to your Mulsanne superpremium sedan if you'd like, but don't expect to be sharing any bubbly with the folks at the World Wildlife Fund if you buy one.

That's because the model's 6,500-pound weight, rear-wheel-drive system and 505-horsepower V-8 engine mean the car gets just 11 mpg/city and 18 mpg/highway. The Mulsanne also only complies with the EPA's Bin 5 pollution standard and California's lowest emissions standard.

"The Mulsanne has got a giant engine, it's not particularly clean in terms of emissions and while it does slightly better than the Mercedes G63 on highway fuel economy, it's certainly not stellar," Vaidyanathan says.

On the plus side, the Mulsanne does go from 0 to 60 mph in about five seconds and boasts a 184 mph top speed. Inside, you'll find such luxuries as a 2,200-watt audio system and leather upholstery that's made from cattle specially raised in cooler climates to minimize bug bites.

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Third-meanest 2014 for the environment: Ford E-150 5.4-liter FFV
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This full-sized van has a 255-horsepower engine, a 6,000-pound test weight and room for eight people, a combination that produces a poor 12 mpg/city and 16 mpg/highway.

Vaidyanathan says the E-150 5.4-liter also complies with just the EPA's Bin 8 emissions standard, "one of the dirtiest out there. The E-150 is particularly poor when it comes to on-road pollution production."

Also see: Here Are the Top Auction Sports Cars of 2013>>

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Second-meanest 2014 for the environment: Bugatti Veyron
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Around $2 million

A base Bugatti Veyron has a 1,001-horsepower 16-cylinder engine and gets just 5.6 mpg/city and 15.1 mpg/highway -- but since the model costs about $2 million, anyone who buys one probably owns an oil field.

Vaidyanathan says the Veyron has the biggest engine of any vehicle on the Meanest Cars list, "and has very poor fuel economy as a result. The car isn't that heavy -- only 4,500 pounds -- but the engine really does the damage in terms of fuel economy."

The Veyron also only complies with the EPA's Bin 5 pollution standard and California's laxest benchmark.

Fortunately for Mother Nature, Veyrons are as rare as they are costly.

French automaker Bugatti plans to build only 450 of them in total and has already shipped some 400. (Current or former Veyron owners reportedly range from magician Criss Angel to hip-hop star Jay-Z.)

Top versions of the model feature 1,200-horsepower engines, go from 0 to 60 mph in 2.5 seconds and have hit 269.86 mph -- a world record for any production car.

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Meanest 2014 Vehicle for the Environment: Ram 2500 (Class 2B)
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Big versions of the Ram 2500 pickup truck weigh 8,500 pounds or more and come with 383-horsepower engines and rear or all-wheel-drive systems that make them great for job sites, but not so hot for the environment.

Add in the fact that the largest Ram 2500s get just 13 mpg/city and 18 mpg/highway and only comply with California's lowest emissions standard and the model "wins" the ACEEE's title for 2014's Meanest Vehicle for the Environment.

Vaidyanathan recommends eco-conscious consumers consider smaller trucks such as the Ram 1500 if those models meet buyers' towing needs. Ram 2500s that weigh less than 8,500 pounds (generally regular-cab versions) also score a little better on the ACEEE's ratings.

"I think that if you legitimately need a Ram 2500 to haul things around, then it makes sense to buy one," Vaidyanathan says. "But there are a number of heavy-duty Rams that people are driving around [unnecessarily], and we're trying to push consumers to buy greener vehicles."

— By Jerry Kronenberg