2012 Mercedes-Benz S350 BlueTEC

When you look at the specs of the Mercedes S350 Bluetec and see that its diesel engine produces only 240 hp, you might think that the two-ton-plus sedan would feel underpowered. Not so, thanks to a prodigious 455 lb-ft of torque. All that torque means that the power is available even at low revs -- from 1600 rpm, in fact -- which means that the S350 doesn't feel slow or sluggish, especially in city driving. And once at speed on the highway, the S350 wafts along effortlessly, effectively insulating you from the baser elements -- noise, vibration, harshness.

Like all S-classes, the S350 exudes all the best Mercedes qualities. It's spacious and luxurious, and its precision German engineering is evident in almost every detail. Best of all, this diesel powerplant promises to deliver better fuel economy than its gasoline-powered siblings' 15/23 mpg city/hwy rating. It might not make you feel as virtuous as if you were driving a Prius, but this is still a car that proves that luxury and economy are not polar opposites.

Amy Skogstrom, Managing Editor

Accelerator response seemed a bit delayed at times, but otherwise the diesel powerplant barely changes the S-class driving experience at all: the car still has plenty of passing power, it still rides and handles amazingly well for a big sedan, and it still immerses its occupants in extreme luxury. Surprisingly, this oil-burning Mercedes-Benz might be even quieter than a gasoline version.

Although I can't come close to affording a car like this, the diesel S-class strikes me like the obvious choice of the S-class lineup. Why? Because it gets fuel economy that's significantly better than the S400 Hybrid, particularly on the highway (the EPA rates the hybrid at 19/25 mpg city/highway, and Mercedes reckons that the diesel will earn a 20/31-mpg rating), but is expected cost only a few thousand dollars more.

Rusty Blackwell, Copy Editor

An S-class and a diesel V-6 might seem like an unlikely couple but Mercedes has created a convincing vehicle with the S350 BlueTec. Because it's a diesel, the engine has a nice throaty undertone that you expect when you drive a $80,000-plus Benz, something that would likely be missing if this were a gasoline V-6. Power is good and fuel economy is impressive for such a big car. My only complaint is that power delivery from the turbocharger could be more progressive at lower speeds.

Jennifer Misaros, Managing Editor, Digital Platforms

Even the upper reaches of the market aren't immune from the pressures of government regulations. The thirstiest sedans in America are rapidly dropping cylinders as pending fuel economy rules force them to travel further on less fuel. BMW already has its 7-series with a gas-fueled twin-turbo six-cylinder that is rated at 17 mpg in the city and 25 mpg on the highway. A supercharged V-6 for the Audi A8 is inevitable.

Mercedes' fuel-conscious flagship sedan is different, though, with a turbo-diesel V-6. Compared to the V-8 S550, the diesel's fuel economy improves significantly from 15/23 mpg to 20/31 mpg. It also delivers imposing off-the-line thrust and remarkable civility that fits perfectly with the S-class character. In nearly every way, the S350 BlueTec creates the same impeccable luxury experience of its more powerful, gas-fed peers. The chief exception is during quick transitions between cruising to mashing the accelerator, when the S350 is sluggish to respond -- it's a combination of slow downshifts and waiting for the turbo to spool up again. True, the 7-series has its own issues with throttle responsiveness, but it does offer a snappier, sportier character.

Although choosing the S350 BlueTec means moving through life at a more leisurely pace, one doesn't have to skimp on luxury. A diesel S-class can be equipped with the same equipment as a $160,000 S600. Our test car was loaded up for chauffer service with a back seat that could make Qatar Airlines' first class look pedestrian. Rear-seat passengers are treated to seats that are power adjustable, heated, and ventilated; individual climate zones; an excellent entertainment system; and power side-window sun shades. Even the front-seat passenger is spoiled with the incredibly slick SplitView front screen that allows the driver to see the navigation screen while the passenger watches a movie. If you're looking for all the luxury of large sedan with a lower fuel bill, the S350 BlueTec is a great car.

Eric Tingwall, Assistant Editor

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