Ferrari 599 GTB Fiorano
Ferrari
Ferrari boasts that its all-new 599 GTB Fiorano has the highest performance of any V12 production car it has ever built. The car also has an average fuel economy of 12.5 miles per gallon.
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updated 1/22/2007 3:31:12 PM ET 2007-01-22T20:31:12

The heroes and villains of fuel economy are as polarizing as Superman and Lex Luthor. Our annual ranking of the most and least fuel-efficient vehicles predictably puts the most charismatically sinister exotic and ultra-luxury models at the bottom and the most frugal and mild-mannered vehicles at the top.

But as polarizing as these lists are, all players will soon take a hit in their EPA-estimated fuel economy ratings. And that’s a good thing. The current, decades-old method that the EPA uses for estimating fuel economy is woefully inadequate, with most projections underestimating fuel consumption by 10 percent to 20 percent. Estimates for gas/electric hybrid vehicles in particular can be bloated even more.

EPA fuel-economy ratings will change entirely when 2008 models reach showrooms in autumn 2007. That's when new test methods for determining the fuel-economy estimates take effect. “The new rating procedures aim to better reflect how we drive in the real world,” says EPA spokesman John Millett.

“The new tests will simulate more-rapid acceleration, higher interstate speeds, cold weather and the use of accessories such as air-conditioning,” Millet says. After the change, the EPA expects all window-sticker ratings to drop. But thrifty, fuel-economy heroes will witness greater declines than profligate fuel consumers. That's partly because high-mileage vehicles have farther to fall. A 10 percent reduction for a car that goes 30 mpg is three times greater than a 10 percent reduction for a car that rates only 10 mpg. “Plus, the smaller engines of the more efficient models typically pay a higher penalty for air-conditioning use at higher interstate speeds,” Millet says.

Still, efficiency advocates don't foresee a reversal of today's movement toward increasingly fuel-efficient cars and trucks. “We don't expect a significant impact on the Toyota Prius’ popularity,” says Doug Coleman, advanced technology vehicle manager of Toyota Motor Sales USA. The Prius, America's best-selling hybrid, is also No. 1 on our 2007 10 Most Fuel-Efficient Vehicles List. “The fuel-economy ratings of conventional gasoline models will also fall, so we expect the Prius to still have strong numbers relative to the segment,” Coleman says.

And even if the fuel-use ratings of gas guzzlers decline by smaller increments than the ratings of fuel economizers, the drop can only discourage consumers who are already wary of fuel costs, says Jon Linkov, Consumer Reports' managing editor for automobiles.

“Consumers have seen large fluctuations in the price of gasoline over the past three years and the sudden depreciation of large SUVs as gas prices rise. According to a survey the Consumer Reports National Research Center conducted in August 2006, fuel economy was a top concern of buyers considering a new vehicle,” Linkov says.

Our ranking includes only 2007 model year vehicles rated by the EPA as of mid-October 2006. That includes most everything on the market today. But the agency does not gauge the fuel use of what it calls “special-purpose vehicles.” That group includes the big Hummer H2. Without comparative data, it's impossible to say if it would make the top 10. Peter Ternes, Hummer’s director of global product communications, says that Hummer engineers average about 12 mpg in the H2 under normal driving conditions, such as commuting to and from work. If that 12 mpg was the H2’s official, EPA-certified fuel-consumption rating, the big SUV would certainly earn a place among the 10 least fuel-efficient vehicles of 2007.

To find the outer boundaries of fuel consumption, ForbesAutos.com reviewed the fuel-economy ratings of every 2007 model year car, truck, van and SUV classified by the government’s Environmental Protection Agency. We used the efficiency ratings in the EPA’s 2007 Fuel Economy Guide published at the official start of the 2007 model year in October 2006.

The vehicles that made the least-efficient list are high-priced and exotic. They don’t sell in large enough volumes to make an impact on national fuel consumption. But Consumer Reports’ Linkov points out that some mass-market models don’t deliver particularly impressive fuel-use ratings either. “In our testing, we found that vehicles such as the Jeep Liberty Diesel, Chrysler 300c, Honda Odyssey, Dodge Ram 1500 SLT Crew Cab 4WD and Ford Focus ZX4 SES had significant shortfalls in their EPA city mileage,” he says.

What’s more, the drivers of gas guzzlers often aren't upset by excessive consumption. “Owner satisfaction is high for some vehicles that don’t get the best fuel economy, such as the Dodge Charger V8, Ford Mustang V8, Chevrolet Corvette and Porsche 911. So not every consumer puts the price of fuel as a top priority when considering a vehicle,” Linkov says.

Our lists start with number 10. Click one of the links above to see how they shake out. Or click here to read our ranking methodology.

© 2013 Forbes.com

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