Mercedes Benz New Diesels:

The Magnificent Bluetec

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We have owned a Mercedes diesel for over 35 years and it has proven both reliable and efficient even with about 500,000 miles on the engine. Since our love affair with our steadfast 240 D we have tested the Volkswagen diesels and found them excellent, and have enjoyed the ones that Mercedes put out a decade ago as well. However, nothing prepared us for effortless and clean running Bluetec that Mercedes is placing in its E 320 sedan and M-Class 320 CDI 4Matic SUV and large R-Class.

If you afford the $50,000 plus price tag this is the way to go, but don’t let that price fool you. The resale on these diesels is going to be awesome for many reasons. First, you get an engine that produces nearly 400 pounds of torque and turns mountains into hills. Secondly, you’ll have lower tune-up costs since a diesel does not have an ignition system per se. Thirdly, the fuel mileage is nearly the equivalent to that of a small hybrid. Finally, they have a well-proven reputation of being good for hundreds of thousands of miles. If you need more convincing, the diesel only costs about a thousand dollars more than the V6 E-Class sedan and it’s going to gain that back when you sell it.

The three-liter V6 engine provides the pulling power of a V8 with the fuel mileage of a subcompact. If you want to challenge your kidneys, you can go over 700 miles before refueling the sedan’s 21 gallon fuel tank. That means at least ten hours without having to stop should you feel up to the challenge. But what is most outstanding is the fact that the Bluetec isn’t smelly or noisy or even difficult to start. You can really only tell it is a diesel at idle and under initial acceleration. Once underway it is easy to get to 60 mph in less than seven seconds in a sedan that weights 4000 pounds.

Seventy years ago Mercedes started producing diesels and they haven’t lost their touch. Even Volkswagen and Audi use their technology. Indeed, if you can wait a bit and settle for a much smaller vehicle, Volkswagen is going to bring its new diesel to market in a couple of years with promises of over 50 mpg.  However, you aren’t going to get the grunt or the luxury of the Mercedes’ 3-liter, V6 turbo diesel with its 4-valves per cylinder, a common rail fuel delivery system pressurized to 23,000-psi and sophisticated turbocharging not to mention the chain-driven balance shaft to keep the hefty unit quiet.

Indeed, the real story here is the  “Bluetec” system. Although it is not available in all states due to environmental restrictions, the engine is kept clean with several scrubbers in the exhaust system in the form of two catalysts and a particulate filter. The first unit is an oxidizing catalytic converter followed by the important particulate filter that gets rid of the smoky exhaust so common to diesel engines. Before exiting the exhaust goes through a final cleaning designed to reduce the nitrogen oxides, which are formed when fuel goes through the combustion process. You can see these oxides as reddish cloud usually above urban areas and/or where heavy equipment is working. Mercedes has a particulate filter that is quite remarkable. When the computer management system senses that the trap is full it turns up the heat in the exhaust causing the particles to be burned off. As well, there is a synthetic urea called AdBlue, which is composed of nitrogen and purified water that is injected into the exhaust to make the diesel more environmentally correct. The replacement of the AdBlue is vital and so potential buyers might want to be aware of this cost.

The E-Class we drove had a 7-speed automatic transmission that was quite abrupt at low speeds. You quickly get used to it, but it does provide a jerk that gets your attention at first. It was present in both the M-Class and the E-Class even with different ratios, weights, and vehicles purposes as the M had all wheel drive. You can shift the automatic yourself, but we didn’t bother. With seven speeds and an engine with such a fat torque curve just letting the transmission do its thing was the logical step even though the Speedshift was easy to use. The transmission is also driver adaptive, too. We elected to use the comfort mode for a smoother take-off as it starts in second gear with this option. Unless you feel the need for speed or just to startle your passengers this is a good choice over the other modes.

Mom’s view: Love at first sniff. No odor, no soot, and no waiting. This is the car for me. The ride is tight; the handling far better than any other diesel, and it has a small turning radius, too. Although I felt the steering was too light, it was very easy to park and on the highway had a good on center feel. You didn’t have to be too attentive with the steering, but when you needed to make a fast correction it was quick to react.

As the ML, it has become too trucky for me. I absolutely adored the first version except for the spartan interior. The newer one lacks cuddle ability, although it is a significant bargain at $41, 680 with a sophisticated array of safety equipment and the same 215 horsepower, 398 lb-ft of torque at a usable 2800 rpm that the sedan offers. That being said, you pay dearly for the gearing and bulk of the SUV as I was unable to better 20 mpg with the air conditioning on despite 21-27 government estimates. Perhaps if I lived where the high stance and seamless all wheel drive system would be a significant benefit I would have snuggled up to the ML more. Or perhaps, it was just the fact that the E 320 sedan was so darn accommodating that it overshadowed the versatility of the M. I can be fickly when it comes to luxury cars and so the ride quality and range of the sedan were its real selling points as well as the great night lighting.

Dad’s view: Outside of a light chattering at idle, the Bluetec is unlike any other diesel we have ever tested or owned. And we have owned a bunch. Using Mercedes’ usual rear wheel drive layout the car feels quite balanced considering that diesel engines are usually heavier due to the sturdy engine needed to contain the high compression ignition. The front suspension is a 4-wheel multilink system and it is assembled along with the engine and steering gear as one unit. This makes for a complex package and one that doesn’t corner particularly well. But this is a luxury sedan and so you can relax knowing you are going to pass that sports car at the next gas station anyway.

Safety wise you get an abundance of airbags here there and everywhere as well as Airmatic semi-active suspension, adaptive damping, speed-sensitive steering, an electronic stability system, a brake assist devise that senses excessive brake pedal input and readies the discs for a faster stop. There are also ABS, traction control and terrific headlights that turn as you corner.

Acceleration is linear, with the best performance coming in passing situations. Getting on a crowded freeway isn’t a problem, but diesels take a while to rev and so it is best to shift the transmission yourself in tight situations. The ride is firm and very comfortable over all road surfaces. The engine sound is well isolated and the E-Class cabin quiet and comfy. As for the M-Class, it just didn’t get the good mileage we expected. We barely got 20 mpg in highway driving with the air conditioning on. As well, the transmission shifts were more immediate and the interior noise level greater probably due to the larger all season tires. I think Mercedes should consider bringing out a smaller SUV as the M-Class is getting too big to be as handy as it once was, although it was very well priced at $43,650 with plenty of standard features.

My feelings about the Bluetec are that is a winner and going to be a hot seller, with just the right touch of frugalness and performance. The E-Class is a perfect home for it, but the M-Class cannot be ignored if you need the larger cargo capacity at a bargain price.

Young working woman’s view: Elegant, understated, wood and leather done with taste, and every control feels like sterling silver rather than silver plate. Of course, I constantly got the cruise control and turn signal stalks mixed up, but an owner would quickly learn the difference. The GPS is too complex for easy use, the seats are almost as good as those in a Volvo or Saab, and the lumbar support is perfectly placed for even us taller folk. The test car had heated seats, a must for me, and Mercedes offers ventilated front seats as well.

You feel like you are in control of a fine yacht as the Mercedes E-Class cheerfully and obediently navigates life’s unpredictable waters. The security of the four year/50,000 mile warranty helps, but be warned that these are not for sale in states that require ultra low sulfur diesel fuel. If you feel the need to be different for over $6000 more you can sooth your fanny with a trim package that includes special paint and Nappa leather surfaces even on the edges of the floor mats.

The E320 Mercedes is not a fashion statement and for some the more blatant BMW 5 Series offers the badly needed attention they seek, but outside of the Command system, a navigation monitor that sits too low to easily read, the poor choice of colors on the GPS and its very complex operating instructions and its slow response this is a perfect car for the professional woman interested in making a statement about individuality and risk taking.

Young man’s view: The GPS sucks. The only good thing is that Mercedes has placed a dandy little LCD screen in the center gauge cluster that is easy to read and well located. The driver’s computer also has a readout that is very clear and provides information on everything, including the satellite station you are on since reverting to the Command system is tedious.

Our test vehicle had the $4000 plus Premium II package that equipped the E-Class with GPS, Sirius Satellite Radio, hands free phone capability, a power rear sunshade, a smart key system, and xenon headlights.  I could live without any of this and found the stereo less than I would have expected. On the other hand I really liked the $500 electronic trunk lid closer. Just press the small button and its lowers or raises itself while you run inside. Most fun to use.

The Harman Kardon 12-speaker 420-watt digital surround-sound audio system has a six-disc in-dash changer capable of playing CDs and MP3 and WMA discs and the whole system is magnificent. This should be a model for BMW. You can even get a readout of the information on your disc. If you feel adventurous try and find the auxiliary input jack. It took me a while before I found it in the glove box. Interesting choice as you can hide you iPod there, too.  As most vehicles of this ilk, hands free cell phone calls are provided for, but you better check and make sure your set works because this isn’t Bluetooth compatible.

Of course the engine is the real story and it is pretty terrific. From experience I know that winter weather and a diesel aren’t necessarily good for each other and we tested these Mercedes in the middle of summer, so I would hold my opinion until my Canadian friends report to me. One notable note is that Mercedes has a website that lists the stations that carry the ultra low sulfur fuel needed. Check it out before you take an extended trip into new territory at

You can’t argue with the benefits this car brings, even at a significant price point. It would be easier to justify the much less expensive ML or even the Chrysler products that are now offering diesel engines in smaller SUVs. Since most of the required fumes cleaning occur in the exhaust system in the form of converters and the use of a urea additive my concern would be the cost of replacing these units. Before buying I would check. Other than that these are very adult vehicles that behave that way. I like a little more pep and so I’d save and buy the CLK 63 AMG convertible and let the sun and wind temper my bad days knowing that in a world of Bluetecs there wouldn’t be any stinky diesel fumes to mar my travels.

Family conference: The perfect engine for the frugal who also want performance. If you love your cake this is the Mercedes to own. Although we found the M-Class too stiff legged and lacking the fuel efficiency we wanted, it still needs to be considered where SUVs can be of benefit. But be warned that if you run the air conditioning and other electronic doodads on a hot day your fuel mileage will drop by ten percent. We don’t know why, especially with all the power the engine has, but that is what happened on both vehicles. Nevertheless, you can easily get subcompact fuel mileage in a luxury sedan with this remarkable Bluetec. If you have to drive to one of the 45 states it is for sale and take a test drive. It is that good.

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Mercedes explanation of its engine

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