Review of midsized luxury sedans

Fuel economy has not usually been a high priority for luxury-car buyers. For paying a premium price, they expect strong performance, a long list of amenities, and a quiet, comfortable cabin. And if that rings up a little higher toll at the gas pump, well, that's just the cost of entry. But erratic gas prices and higher federal fuel-economy standards on the horizon are increasingly making automakers look for ways to improve gas mileage even in this category.

The four cars we tested for this issue—the Audi A6, Infiniti M35h, Mercedes-Benz E350 BlueTec, and Saab 9-5—approach the goal in different ways. (See our full Ratings of sedans, available to subscribers.) Those include hybrid and diesel drivetrains, lightweight materials, seven- or eight-speed automatic transmissions, and supercharging and turbocharging, which lets a car squeeze more power from a smaller engine. The result: Gas mileage for the group is among the best in the category, although the cars' overall performance varies dramatically, from the top-rated Audi to the bottom-rated Saab.

Redesigned for 2012, the A6 is significantly improved and now ties the Infiniti M37 for the top spot in this class. Its overall road-test score has jumped to 93 from its previous 79, thanks to an inviting combination of strong acceleration, agile handling, a comfortable ride, and a quiet, well-finished interior. Moreover, the A6's supercharged V6, new eight-speed automatic transmission, and slightly lighter weight help boost its fuel economy to 22 mpg overall, even with all-wheel drive.

The fuel-economy champ in this class is now the E350 BlueTec, which is powered by a 3.0-liter V6 diesel engine. Its 26 mpg overall edges out the M35h's 25 mpg and is much better than any luxury sedan with a conventional gasoline engine. The trade-off is some engine noise at low speeds. Our tested car, equipped with Mercedes' Luxury package, is a comfortable, quiet, agile, and luxurious sedan that ranks just below the leaders in this category.

The M35h is Infiniti's first hybrid, and it shows teething pains. The gas-electric system helps deliver quick acceleration and fuel economy that's on par with some four-cylinder family sedans, but its power delivery tends to be jerky and abrupt. In addition, the M35h's handling and braking are not quite up to that of the conventional M37. All of that detracts from an otherwise outstanding package.

The redesigned Saab 9-5 is disappointing in this class. It shares a platform with the Buick LaCrosse and Regal, its former GM cousins, but the 9-5 doesn't measure up well to those models or its competitors. The turbocharged four-cylinder engine in our test car—the most frequently chosen engine—returns 22 mpg, the same as the A6. And although the 9-5 has excellent fit and finish and secure handling, it has a noisy engine, stiff ride, impaired visibility, and relatively slow acceleration.

Prices for this group range from the 9-5's $46,655 to the M35h's $58,655. None of these cars is recommended. The 9-5 didn't score high enough, and the others are too new for us to have reliability data.

See our full Ratings of sedans, available to subscribers.

This four-door crossover-type SUV is larger and taller than the familiar Mini Cooper, yet it still has the agility and frisky character of its siblings. It also achieved an excellent 26 mpg overall, which is better than any nonhybrid small SUV we've tested. But a stiff ride, a noisy cabin, and confusing controls limited its overall road-test score to 66. Read our full review of the Mini Cooper Countryman S (available to subscribers).