When it comes to the market's least fuel-efficient cars, what costs us cash at the pump also draws stares at the stoplight.
Consider Ferrari's recently released 599 GTB Fiorano coupe, which is priced at around $250,000.
The car has a 620-horsepower, V-12 engine. It is Ferrari's most extreme performer — basically a street-legal race car — so of course it burns fuel like a 747, getting 11 miles per gallon in the city.
Ferrari probably expects the vehicle to be on a list of gas guzzlers, and most likely doesn't care; economy is not the point of the 599. Nor is it for another of the market's least fuel-efficient cars, Lamborghini's 12-cylinder Murciélago two-door, which costs around $290,000 and gets nine mpg in the city.
Our list of the least fuel-efficient 2007 model cars, according to recently released data from the U.S. Environmental Protection Agency (EPA), includes such other beauties as DaimlerChysler's $390,000 Maybach 62 luxury sedan and BMW's $100,000 M6 hot rod.
But not all fuel-inefficient autos were included. That's because it's early into the 2007 model year, and the EPA has not yet published fuel economy figures for all cars.
For example, General Motors' notoriously wasteful Hummer H2 doesn't appear because the EPA has not yet issued the car a 2007 model ranking. And because of varying fuel economy estimates from different sources, we chose the EPA as the official — and only — source for data in this story.
What's more, we only included autos with their original equipment — no vehicles modified by others after they rolled off assembly lines are on the list. For example, we did not look at the customizations that California's Saleen makes of Ford Motor's Mustangs. And in evaluating a model's ranking, we only considered one entry per nameplate: the least-efficient one.
For example, we included BMW's 6 Series line of coupes and convertibles, but that's because the M6, the flagship of the 6 Series line, gets 12 mpg in the city. We did not look at the other, more-efficient models within the 6 Series family in formulating our list.
We ranked the vehicles in our story based on what it costs to fuel them per year, according to the EPA. In calculating a car's annual fueling cost, the EPA assumes you will drive it 15,000 miles per year. The EPA also takes into account the current price of fuel. For this story, average first-quarter fuel prices were used to estimate the annual cost.
We measured cars by fueling cost because the EPA lists two gas mileage figures per car, city and highway mileage, and we did not want to make an arbitrary decision about which mileage figure is more important. When you buy a car, your daily driving routine will determine whether city or highway mileage is more important for you.
While hard-core sports cars and opulent luxury cars tend to have bad mileage, some of the vehicles on our list are old, heavy models with inefficient engines. Chevrolet's $23,000 Express van, which is tied for fourth place on our list, is one example.
But you might be surprised by another leading cause of bad mileage: ethanol fuel, an alternative to traditional gasoline.
Many American cars are able to run on both gasoline and ethanol. But ethanol is less energy-dense than other fuels, so it reduces fuel economy by 25 percent to 30 percent. Many of the cars on our list — particularly the American cars — can run on ethanol or gasoline, and the ethanol-powered cars tend to be less fuel-efficient than their traditional counterparts.
But in some cases, the vehicles on our list are simply there because they are SUVs or pickups that use big, powerful and, yes, inefficient V-8 engines.
A vehicle like Cadillac's Escalade SUV, which is tied for seventh place, has everything you could want in an inefficient car: huge size, a hefty curb weight, a huge engine — and lots of sex appeal.
General Motors recognizes that economy is not the purpose of a car like the Escalade, but spokeswoman Sherrie Childers Arb points out that the company also offers "24 models that the EPA rates at 30 mpg or better on the highway."
Toyota Motor defended the inclusion of the Toyota Land Cruiser SUV. In an e-mail message, company spokesman John Hanson said, "There are many vehicles with the same annual fuel cost in this list. So this list is not just 10 different models. It is approximately 80 models, made up of mostly large SUVs, large pickups, passenger vans and high-performance luxury/exotic cars. By their nature, heavy and powerful vehicles will get relatively lower fuel economy."
Audi took issue with our practice of naming an entire model range if one of the range's vehicles had poor fuel economy. For example, Audi's A8 sedan is on our list, but due to space constraints we did not specify which engine/transmission combination earns the model bad marks for gas mileage. We provided a link to that information in each slide.
But David Greene, corporate fellow at the U.S. Department of Energy's Oak Ridge National Laboratory, says that engine/transmission combinations are not the only things that affect fuel economy. (Greene is the person in charge of operating the department's fuel-economy information program.)
"There are a number of things," Greene said. "The EPA has a fairly elaborate set of rules. It's not only the body style, the engine and the transmission. Those are the most important three factors, but there are other factors."
Of the two Land Rovers on our list, spokeswoman Deborah Sandford says that "Land Rover vehicles are designed to have a breadth of capability that meets our owners' use both on- and off-road. We are continuously working to improve our fuel economy without compromising our brand attributes."
As for the long, heavy Rolls-Royce Phantom sedan, which is also on our list, Rolls spokesman Bob Austin wrote, "While it is a fact that in a spectrum of all new cars the Phantom is at the high end in fuel consumption, it is relatively fuel-efficient for its size. It gets 13 mpg city and 19 mpg highway — much better than most sport utility vehicles that are similar in size."
One of Rolls' main competitors, Bentley, thinks annual fueling cost figures "are irrelevant as they relate to Bentley owners," according to company spokesman David Reuter. He also said that fueling cost data are "computed based on 15,000 average miles driven per year. That figure is substantially higher than what a typical Bentley owner would drive his or her car. A typical Bentley owner would drive his or her vehicle less than 7,000 to 8,000 miles per year. Mostly, this is because Continental owners have a fleet of four or five other vehicles, while an Arnage/Azure owner has as many as seven or eight."
He added, "Bentley Motors is committed to producing more fuel-efficient cars in the future, and we are currently developing new technologies to help us achieve this. We are in the early planning phase of a long-term strategy to examine all options, including hybrids and diesel engines, and we are not ruling anything out at this stage."
Tony Fouladpour, a spokesman for high-end automaker Porsche, discussed the inclusion of the company's Cayenne SUV on our list. "All the new Cayennes now use the direct-injection technology that is 15 percent more efficient while offering a corresponding increase in power — the type of engine performance expected in Porsches," he wrote. "While this doesn't translate to lower costs in fueling, it does serve to maintain the cost with significant improvements in performance."
Ford Motor declined to comment for this story. By publication time, the other manufacturers mentioned in this story had not responded to requests for comment.
© 2012 Forbes.com