Click the E320 BlueTec for a high res gallery

Mercedes-Benz is quite literally the first name in diesel. The 1936 Mercedes 260D was the first production passenger car powered by a diesel engine. Daimler has been building diesel cars and trucks pretty much continuously ever since. Along with Volkswagen, Daimler has also been the primary purveyor of diesel vehicles in the US market over the past three decades. The current E320 BlueTec traces its roots back directly to the 300D of 1976 and is on the verge of being replaced with an all-new model for 2010.

The E-Class is Mercedes' mainstream mid-sized luxury sedan and is second only to the smaller C-class in US sales volume for the brand. Several new diesel technologies have debuted on the E and its predecessors over the years including common rail and injection and turbocharging. Since the car we tested is near the end of its life cycle this one wasn't the most up-to-date example, but it's still a good sampling of a modern diesel car. See what we thought of the E320 after the jump.

Photos Copyright ©2008 Sam Abuelsamid / Weblogs, Inc.

I picked up the E320 at the airport upon my return from a trip to the west coast trip and Arizona to drive the new Ford Fusion hybrid, the Mustang and the Honda Insight (that report is coming soon). Even though Arizona was surprisingly cold, Detroit was downright frigid. Fortunately the E320 was equipped with all the accoutrements one expects in a modern "executive sedan," including heated seats that I quickly cranked up to the maximum settings.

Back in the bad old days of diesel engines, one of the numerous complaints that drivers had was cold temperature starting. Because the diesels rely on the heat generated by compressing the intake air charge to ignite the fuel, they are equipped with glow plugs that pre-heat the cylinder walls before starting. That meant you might have to wait anywhere from 10-30 seconds for the glow plug light to go out before cranking the engine. Not so anymore. Even with temperatures that dipped to the low teens or single digits, the direct injected Mercedes diesel fired up instantly every time.

The current generation E-class debuted in 2003 on what Mercedes internally refers to as the W211 platform and got a mid-cycle refresh in 2006. The 3.0L diesel V6 debuted in 2005 first as the E320 CDI and two years later became the E320 BlueTec that we spent a week with. When the E320 BlueTec was introduced in 2007, it was touted as the first new diesel vehicle to be available in California in several years (which needed a caveat). BlueTec is Daimler's branding for "clean diesels" but doesn't refer to any specific technology. For example the new ML320, GL320 and R320 BlueTec models all use urea injection in addition to a particulate filter for exhaust after treatment to meet Tier 2 Bin 5 emissions standards.

The engine in the E320 is essentially the same V6 found in the SUVs and has common rail injection, a variable nozzle turbocharger, exhaust gas recirculation and that particulate filter. However, rather than adapt the urea system to a car near the end of its life-cycle, Mercedes used a lean NOx trap similar to the setup used by Volkswagen for the Jetta TDI. That means the NOx emissions are much lower than the previous CDI model, but they don't reach the level required for T2B5.

The redesigned 2010 E320 that is debuting next spring will get the full urea treatment but for now, the E320 still does not technically meet the standards of California and four other states. California granted a waiver to Mercedes allowing the cars to be leased there for up to three years but after the leases are up they cannot be resold in that state.

Over in Europe, E-class sedans and wagons often powered by relatively small four cylinder diesel engines are the ride of choice for cab drivers, much like the old Ford Crown Vic is here. Americans don't get access to those low rent Benz models. Instead, our black tester had the MB Tex faux hide interior. Back in the day, there was never any doubt when you climbed into a car with vinyl seats that you were sitting on something utterly foreign to nature. MB Tex is something else altogether. Admittedly, this is not the kind of buttery soft and rich kind of leather you might find in a Bentley, but the uninitiated observer will have a very difficult time distinguishing this from more pedestrian hides.

As one would expect of a German sedan with a price point starting north of $50,000, the E320 is very well equipped. The MB Tex is accompanied by gorgeous burl walnut trim on the dash, console and steering wheel. Electronic goodies abound including a Harman/Kardon audio system with direct iPod and auxiliary jack connectors in the glove box. Dual zone climate control allows the front seat occupants to select their own comfort levels. Everything was nicely aligned and seemed tightly screwed together.

During the week that the E320 was in the ABG garage, I had to make a couple of trips to the far side of the metro Detroit area from my Ypsilanti home. The cabin of the E320 proved to be a very pleasant environment for conducting these drives. The pleasantly thick rim of the steering wheel is adjustable for both height above the lap and distance from the chest. The instruments are clearly marked in a simple white on black and very easy to read. An LCD display in the central part of the speedometer allows the driver to page through data using a button on the left side of the steering wheel hub. The diesel E-class doesn't get any paddle shifters, but those who prefer to manipulate the automatic transmission can do so with a left-right of the lever from the D position, much like a Chrysler vehicle. The second row has room for three although the center occupant will find their feet straddling the drive-shaft tunnel.

On the road, the E320 provides a quiet and comfortable environment although it's not quite the bank vault that the S-class is. The diesel engine, like those from its German competitors, is as smooth and quiet as any gasoline engine. The E320 is certainly no featherweight at 3,820 lbs, but it does fall about mid-pack compared to competitors from BMW and Audi. The 210 hp from the diesel V6 sounds modest, but the 400 lb-ft of torque from 1,600-2,400 rpm is more than enough authority, and owners will never feel inadequate when merging onto freeways. Mercedes quotes the E320 0-60 mph time as 6.6 seconds which conforms with our seat-of-the-pants impressions.

The torque gets sent to the rear axle via a 7-speed automatic transmission with the aforementioned Touch-Shift. Frankly, the manual shift mode can be ignored since its left-right tap setup has never felt natural on any car so equipped. However, those with a more sporting bent might want to take note of the C/S button to the left of the shifter. This switches things from comfort to sport mode. In the default comfort mode, the transmission's shifts feel generally a bit lazy but they are smooth. Switch over to sport mode, and ratio changes become snappier, especially the down shifts when the accelerator is pressed. When braking, the sport mode also induces down shifts during braking to provide some engine braking and have the engine in the meat of the torque range to accelerate out of corners.

Part of that mid-cycle refresh in 2006 included discarding the electro-hydraulic brake by wire system that the E-class had at launch. That brake system caused Mercedes and its customers no end of grief and recalls during the time it was used. The E-class and other Mercedes have now reverted to a conventional system equipped with ABS/TCS and stability control. During the snowfalls that we got while the E320 was with us, the stability control proved to be much smoother and more seamless in its operation than the systems that Mercedes pioneered a decade ago. Those systems were abrupt and aggressive in their control, but now the car just goes where you point it (within the limits of adhesion of course) with nothing more than a flashing light to tell you that it is active.

So what of fuel efficiency, one of the main reasons for driving a diesel? The E320 did very well here as well. Over the week of driving, it averaged 29 mpg overall in a fairly even mix of city and highway driving with no real attempts to maximize efficiency. The EPA rates the E320 at 23 city, 32 highway and 26 combined. Considering the cold weather we experienced, the performance of this nearly two ton car was admirable. During freeway cruising, the mileage generally averaged about 35-36 mpg. Overall, the E320 beat the EPA sticker by about 12 percent without having to resort to any light foot or drafting tactics.

As one might expect of a German luxury sedan in America, the E320 doesn't come cheap. The $54,200 base price climbed to $58,345 with options and delivery. That's not out of line with competitors but in this economic environment it's certainly more than most people can afford. We'll be getting a preview of the new 2010 E-Class just before the Detroit Auto Show, and it will have its official coming out at the Geneva show in March. When the next gen E320 goes on sale in the fall, it will have the urea injection system that makes it fully compliant in all 50 states.

Photos Copyright ©2008 Sam Abuelsamid / Weblogs, Inc.

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