1. Bugatti Veyron: 8 mpg city/15 mpg highway, premium gas
With 16 cylinders producing 1,200 hp, it's something of a miracle that the Veyron doesn't report its efficiency in gallons per mile. The typical Veyron owner drives less than 1,000 miles a year, and the production run has now ended, so the era of the Veyron as America's least efficient vehicle will be coming to a close.
2. GMC Yukon XL 2500 4WD/Chevrolet Suburban 2500 4WD: 10 mpg city/15 mpg highway, regular gas
3. GMC Yukon XL/Chevrolet Suburban 2500 2WD: 10 mpg/16 mpg, regular
These graybeards of the full-size truck-based SUV market will gain major improvements in fuel economy when new versions arrive in a couple of years. Until then, they're still often seen as family vehicles in rural locales, and if driven 15,000 miles a year, each one will belch nearly 12 tons of carbon dioxide into the atmosphere.
4. Ferrari FF: 11 mpg/16 mpg, premium gas
Two decades ago, the least-efficient vehicles in America consisted almost entirely of high-end sports cars, especially European models. Today, there's only one Ferrari on the list, the V-12-powered, 660-hp FF — which can be bought with an optional stop-start system.
5. Ford Raptor: 11 mpg/16 mpg, regular gas
Like most vehicles on this list, the all-terrain Raptor was designed with fuel economy as a distant afterthought to some other goal, namely rolling through desert trails at top speed. Yet it's worth remarking on the penalty such traits carry in real life; by the EPA's estimate, driving the Raptor 25 miles requires nearly two gallons of gasoline.
6. Lamborghini Aventador: 11 mpg/18 mpg, premium gas
Twelve-cylinder engines have been synonymous with luxury and power for a century, from the first Packards and Rolls-Royces to the BMW 750iLs on Craigslist. Yet the end of the 12-cylinder engine may be on the horizon; tighter fuel economy rules around the world have forced automakers to turn to forcing more air through smaller engines with fewer efficiency-sapping parts. For 2013, the Aventador received a stop-start system and cylinder deactivation, allowing it to run at slower speeds with just half of its 6.5-liter V-12 burning fuel. That tech netted all of one mpg in the car's highway fuel economy ratings.
7. Bentley Mulsanne: 11 mpg/18 mpg, premium gas
At $290,000, Bentley's largest sedan also claims the title of the most expensive midsize car for sale on these shores. Like the Lamborghinis and Bugattis, the Bentley will likely see only a few thousand miles of use a year. The big Bentley also shares something else with those makes; its corporate parent, Volkswagen, which has to balance out the efficiency failings of a handful of ultra-luxury cars with sales of more efficient models to
everyday customers.
8. Mercedes-Benz G63 AMG: 12 mpg/14 mpg, premium gas
9. Mercedes-Benz G550: 12 mpg/15 mpg, premium gas
Combining the brick-like shape of an SUV with a massive motor for rapid transit always means bad things for efficiency. The G550, the old-fashioned gelandewagen that's now a throughly modern Mercedes. While the base G550 — sticker price, $114,000 — gets 388 hp from its 5.5-liter V8, the turbo version of that motor in the G63 AMG generates 544 hp, with only a one-mpg penalty on highway travel. If you're going to burn that much gas, you might as well make the most of it.
10. Ford F-150 4WD, with 6.2-liter V-8: 12 mpg/16 mpg, regular gas
This kind of full-size, V-8 powered pickup has started to wane in popularity; most pickup buyers don't need the largest gasoline engine available, and if they require that much grunt, it's easier to step into the diesel-powered heavy-duty size. But there's still thousands of Americans who not only buy this kind of ride but use it as their daily driver, often unloaded. While the Ford V-8 barely makes the list, it's competition is only a few miles-per-gallon more efficient. The concept Ford Atlas unveiled at the Detroit auto show featured several tricks meant to improve full-size truck fuel economy, like shutters in the wheels. Looking at the upcoming rules against what's on sale today shows truck builders will need every bit of magic they can conjure.
