Kicking things off this beautiful Wednesday morning comes a batch of Mercedes reviews that analyze two of Mercedes' new "Blue" models:  the S400 BlueHYBRID and the ML320 BlueTEC.  A grand total of three articles are dedicated to the pair, with each seeking to determine whether or not the Blue models are worthy alternatives to their traditional gasoline only-powered counterparts.

As is the case with all our Mercedes Review Roundups, you can find excerpts from each review as well as links back to the full articles immediately below.

Enjoy ladies and gentlemen.


Mercedes-Benz S400 BlueHYBRID (via Autoweek)
Reviewer's rating:  Unspecified

"When it goes on sale in North America in September 2009, the S400 BlueHybrid likely will cost about the same as today's S550. The problem is, to the average shopper, it looks like the three-year-old S350. You can look for aerodynamic amendments or changes in ride height, but you'll be looking in vain. Only subtle BlueHybrid badges on the flanks and the trunk lid signal the high-tech driveline. Keener observers will spot new wheels and tires: 18-inch alloys with low-rolling-resistance Continental Contact 235/55R rubber.

Underneath, a lightly reworked version of the existing Mercedes 3.5-liter V6 gasoline engine gains a new cylinder head, lightweight pistons and a reprofiled camshaft for altered valve timing. It does without the direct injection used on the CLS350's similar V6. Output increases by just 7 hp over the S350, at 279 hp, with torque remaining the same at 258 lb-ft.

Those are not dazzling figures for a car that weighs 4,383 pounds. But a three-phase AC electric motor, mounted within the front of the gearbox housing, provides additional thrust when required. The S400 BlueHybrid's peak output swells to 299 hp and 284 lb-ft, with drive channeled to the rear wheels via the standard Mercedes seven-speed automatic. The new system does not support pure electric propulsion like that offered by the LS 600h; the efforts of the electric motor are used exclusively to assist the gasoline engine.

Mercedes expects that the S400 BlueHybrid's advanced new lithium-ion battery will be the envy of rival carmakers. Weighing 60 pounds and made up of five cells, the battery pack uses a chemical process based on nickel-cobalt-aluminum. This, Mercedes claims, provides more efficient charging and improved discharge properties compared with the nickel-metal-hydride technology used in most hybrids. It also is incredibly compact, so much so that Mercedes has managed to mount the battery in the position usually reserved for the S350's standard lead-acid unit at the base of the windscreen, where it is cooled by a patented process linked with the car's air-conditioning system, keeping it operating within an optimal range between 59 and 95 degrees Fahrenheit.

The battery stores electricity created under braking and when coasting, during which the S400 BlueHybrid's electric motor functions as a generator. Other fuel-saving measures include an integrated stop/start system, in which the gasoline engine switches off when the driver engages the brakes at speeds of less than 10 mph and then automatically restarts when the accelerator is depressed.

The S400 BlueHybrid doesn't demand any change in driving style as some hybrids do. It feels much like the S350, only a touch more powerful under acceleration in lower gears. Around town, the stop/start system works well, the electric motor providing almost instantaneous start-up after the engine has been automatically switched off at traffic lights and such. On the open road in upper gears, the added output is not immediately evident, in part because of the added 165 pounds of the hybrid system. Power delivery is smooth and seamless, with or without electric assist. What stands out is how fast the battery charges; one long, downhill stretch is enough to see it charge at almost 100 percent."

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Mercedes-Benz S400 BlueHYBRID (via Inside Line)
Reviewer's rating:  Unspecified

"As you'd expect from a mild hybrid, the V6 gasoline engine switches off when you touch the brakes and roll to a standstill at speeds below 10 mph, and then automatically restarts again the moment you depress the accelerator. Still, if the S-Class had its hybrid badges deleted, you might just think you were driving a standard S350 with a particularly lively engine.

When we drove a prototype version of the new sedan around the hills of Stuttgart not far from Mercedes-Benz's headquarters in Germany, there were only subtle hints to its advanced drivetrain. The best thing about the S400 BlueHybrid is its seamless power delivery. There might be two different power sources at work, but the way they come together to provide one long, linear surge of hushed acceleration, with just a distant hint of V6 growl if you've really got your right foot planted, is deeply impressive.

Acceleration is brisk, but this is no performance car. Put that down to added weight brought upon by the electric motor, lithium-ion battery pack and associated hardware, all of which add 165 pounds to the car. Mercedes-Benz claims the S400 BlueHybrid accelerates to 100 km/h (62 mph) in 7.2 seconds, just 0.1 second quicker than the S350.

Where it really begins to makes sense, though, is at the gas station. With combined fuel consumption on the European cycle of 29.8 mpg, the S400 BlueHybrid betters the S350 by 7 mpg — enough to provide a 165-mile boost in cruising range from its large 23.8-gallon tank to 708 miles.

The S400's stop-start system is ultra-quick to respond and doesn't impede progress at traffic lights. Steering and air-conditioning also remain functioning, as they've been modified to run exclusively on electricity. The regenerative brakes don't win any awards for feel, though, as the transition from regen mode to mechanical braking still feels unnatural.

For all its low-speed theatrics, it is on the open road where the S400 BlueHybrid feels most at home. This is an S-Class, after all. And since the battery pack and electric motor represent a negligible weight increase, there's no apparent change in this car's dynamic capabilities. The multilink suspension with air springs delivers a comfortable ride, although it doesn't lower its ride height automatically at speed like the Lexus LS 600h L. There's also very little tire roar from these low-rolling-resistance 225/45R18 Continental Contact tires.

Inside, there's little to distinguish the S400 BlueHybrid. An altered instrument display keeps tabs on the flow of electricity in and out of the lithium-ion battery pack, and there is a small hybrid badge on the center console. Otherwise, it is business as usual: acres of space, supreme seating comfort, a near perfect driving position and the famed Mercedes refinement. "

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Mercedes-Benz ML320 BlueTEC (via Inside Line)
Reviewer's rating:  Unspecified

As diesels go, the 2009 Mercedes-Benz ML320 Bluetec is fairly quiet. There is a low diesel rumble when you put your foot down, but it can easily be drowned out with music (ah, thank you, modern technology). If you want to be alone with your thoughts or like to drive with the windows down, you'll just have to get used to it. It's not loud and obtrusive, but it is there, like the low vibrato of a contralto.

The ML320's 3.0-liter V6 diesel engine features a lightweight aluminum block, a forged-steel crankshaft, cylinder heads with four valves per cylinder, and an internal balance shaft to control the vibration created by the diesel's tall 16.5:1 compression ratio. A variable-nozzle turbocharger spins quickly to reduce turbo lag and then helps deliver 210 horsepower at 3,800 rpm and 398 pound-feet of torque at 1,600-2,400 rpm.

The diesel V6 is mated to a quick-shifting seven-speed automatic transmission with the same column-mounted shift lever you'll find in the Mercedes R-Class, although there are also shift paddles mounted on the steering wheel. With seven gears, programming for maximum fuel-efficiency, a relatively narrow power band and a redline of only 4,500 rpm, the transmission always feels full of activity, but it's smooth and quick to react at least.

In normal city driving, the ML320 Bluetec's powertrain had plenty of power, although it didn't really develop any urgency until the torque peak came within reach. At the test track, where we try to ring out every precious second, the ML320 would launch like a Nissan GT-R and achieve 30 mph in a heartbeat, but then it would realize that such behavior is unseemly for a turbodiesel and finally reach 60 mph in 8.5 seconds (8.2 seconds with 1 foot of rollout like on a drag strip). It hit the quarter-mile in 16.2 seconds at 83.3 mph.

Of course, we can't drag race like this at every traffic light, so we must admit that in everyday driving we found the ML320 Bluetec to be a little slow. We had no problems getting up to speed on freeway on-ramps or while passing on the highway. It was just that laziness after 30 mph that bothered us.

Meanwhile the ML320's 13-inch disc brakes prove pretty effective with the relatively wide 255/50R19 Bridgestone Dueler H/L 400 tires and helped bring this 5,129-pound Benz to a halt from 60 mph in 121 feet. The brake pedal feels mushy underfoot as if it's not really connected to anything; nevertheless, there's plenty of stopping power and very good resistance to fade."

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