Diesel vs. Gas
Why should you even consider a diesel? Diesel engines, which historically have been dirty (in terms of tailpipe emissions), are also inherently more efficient than comparable gasoline engines, so they burn less fuel to achieve the same ends. Theoretically, this saves you money. Also, the amount of fuel burned is proportional to the amount of carbon dioxide released, so any time you're burning less fuel you're contributing less greenhouse gas to the atmosphere. All we ever needed to do was fix the other environmental problem, the pollutants — mainly soot and oxides of nitrogen. Thanks to ultra-low-sulfur diesel fuel, which is relatively new in the States, we can now use exhaust aftertreatment that has been employed in Europe for years. As a result, the E320 Bluetec is the cleanest diesel car sold in the U.S. That's been the case since 2007, when it replaced the 2006 E320 CDI (practically the same car but not quite as clean). Volkswagen pulled its diesels from the market to clean them up in time for 2009.
Technically, the Bluetec isn't sold in California, Connecticut, Maine, Massachusetts, New Jersey, New York, Rhode Island and Vermont — all of which follow California's stricter pollution limits. In California, though, Mercedes worked out a deal to offer a limited number of E320 Bluetecs through a two-year/24,000-mile lease. (Later this year, when Bluetec technology with urea injection hits the company's SUVs, they will be sold in all 50 states. The E-Class won't be 50-state compliant until it's redesigned for 2009 or '10.)
As is usually the case with luxury cars, even the base engine — a 3.5-liter gasoline V-6 — is plenty powerful, capable of 0-60 times of just 6.5 seconds, according to Mercedes. As the table illustrates, the diesel has less horsepower than the V-6 gas engine but more torque than the V-8 gas engine. Torque is important, and nowhere is that clearer than in the Bluetec's 0-60 time, which is a mere tenth of a second slower than the E350 gas version.
|E320 Bluetec||E350||E550||E63 AMG|
|Base list price||$52,200||$51,200||$59,700||$85,300|
|Engine type||turbo-diesel V-6||V-6||V-8||V-8|
|210 @ 3,800||268 @ 6,000||382 @ 6,000||507 @ 6,800|
(lbs.-ft. @ rpm)
|258 @ 2,400-|
|391 @ 2,800-|
|465 @ 5,200|
|EPA-estimated MPG (city/highway — combined)||23/32 — 26||17/24 — 19||15/22 — 17||12/19 — 15|
|regular gasoline*||regular gasoline*||regular gasoline*|
estimated 0-60 mph (sec.)
|*Premium gasoline recommended for performance specs shown. |
Source: Manufacturer data
By the numbers, one of the advantages is clear: combined fuel economy of 26 mpg compared to the most efficient gas engine's 19 mpg. But then there's the issue of fuel cost. You may have noticed that the pendulum of diesel fuel — which historically has cost less than gasoline — has swung the other way. Mathematics are in order: The week preceding this report saw ultra-low-sulfur diesel fuel prices averaging $4.71 per gallon in the U.S. Premium gasoline cost $4.20 on average. That's 12 percent more for diesel. The E320 Bluetec's mileage is 37 percent higher than the gas-powered E350, so there's a definite advantage on a tank-by-tank basis, at least for this model. (Even if you ran the E350 on regular rather than premium gas at last week's $3.98 average price, the diesel would be 18 percent more expensive — low enough to be offset by the Bluetec's higher mileage.)
Similar to hybrids, diesel drivetrains tend to cost more than comparable gas-only versions. It's true here, too, but the E320 Bluetec's price premium is exactly $1,000. Not bad. Unfortunately, there are other shortcomings to diesel, not the least of which is a scarcity of filling stations. In most areas of the country you can find diesel fuel ... but you have to look. The upside is that you'll do so less frequently thanks to the Bluetec's higher efficiency; theoretically, you can go 485 miles of all-city driving or 675 miles on the highway between fill-ups. The biggest problem I see with investing in a diesel is the unknown. As Americans are finally figuring out, there's no promise that gas will ever become cheap ... or stay cheap for long ... or do anything but continue to climb in price. Likewise, there's no telling what will happen to diesel fuel prices. They could come down closer to gas, or they could skyrocket beyond comprehension. We just don't know, and it's out of the buyer's control.
Beyond the general downsides of buying a diesel, I found a critical downside to the E320 Bluetec: accelerator lag. To be clear, the car really moves out ... once it starts moving, but oftentimes it takes too long to do so after you tromp on the accelerator. From a standing start or when in motion, the engine regularly waits a beat or two to respond. This could be turbo lag, electronic throttle lag, transmission lag or some other kind of lag not yet discovered by man, but it's lag and I consider it a serious problem, as I do in gasoline-powered vehicles that exhibit the same behavior. I've experienced degrees of the same in other Mercedes models, such as the ML320 CDI sport utility that uses this engine, but it's not a characteristic of diesels overall.
Going & Stopping
Accelerator lag notwithstanding, the E320 Bluetec's drivetrain gives up nothing to the gas type; in fact its high torque at low engine speeds makes for confident, drama-free acceleration. The engine's sound is different, but not by any means noisier than the gas V-6; in fact, the latter has to rev higher and work a little bit harder to get a move on, so in some instances you're more likely to hear that one than the diesel. Overall, though, the cabin is very quiet.
The seven-speed automatic transmission is so smooth it fades into the background. Shared with the gas models, this transmission has a button on the center console marked C/S that selects between two drive modes, Comfort and Sport. Comfort is a word that makes sense when applied to adjustable suspension firmness, but I don't think there's anything uncomfortable about the Sport transmission mode. What Sport does is hold onto lower gears until higher up the engine's rpm range, which keeps power at the ready. It also makes the transmission kick down more readily when you jab the accelerator. The tradeoff to this mode is lower fuel economy. C mode is more conservative with the shifts, and might better be called E for Economy or Efficiency.
By knocking the gear selector left or right you can downshift or upshift, respectively, but this isn't a true sequential-shifting, or clutchless manual, feature like some cars offer because it doesn't hold a gear. It simply locks out the gears above the one selected, and the trans shifts freely among the lower gears. It's no different than the "4321" settings that still follow the D in some cars' PRND4321 shift range. Mercedes doesn't offer a manual gearbox for the E-Class.
I had to adjust to my test car's pushbutton ignition, which allows you to leave the keyfob in your pocket. The concept isn't a new one, but this car's start/stop button tops the gearshift knob, and the previous car I tested had a button in the same place that had to be pushed before moving the lever. Time after time, I went to move the transmission out of Park, pushed the button and killed the engine. After a few days I got past it, but if you own two cars — one of each type — you might want to bank some spare funds to replace your starter motor twice as often.
Compared to the V-6, the gas V-8 propels the car even more effortlessly, but you'd have to be a serious leadfoot to sign on for the E550's 17 combined mpg when the fuel-cost game has changed as much as it has.
Relieved of the numb Sensotronic electro-hydraulic brakes that accompanied this E-Class generation's debut, it now has effective, agreeable antilock four-wheel disc brakes that do the job as expected. (The "by-wire" braking system was discontinued from the E-Class and CLS-Class because of reliability problems, but the overarching problem was that they felt like you were trying to brake with your foot wrapped in a sponge. Sensotronic now plagues only the SL-Class and SLR McLaren supercar.)
No Sport Sedan
There may be a Sport mode on the transmission, but if you're looking for a luxury sport sedan, the E-Class isn't it. The luxury is there, and it's hard to argue with the AMG version's sporting capabilities, but overall the E's handling and braking don't compare to those of the BMW 5 Series or Jaguar XF — or even the Acura TL, Audi A6 or Cadillac STS. Across the board, when I think of "drivers' cars," the Mercedes brand doesn't come to mind. I'm not quick to generalize, but I'm comfortable with this one.
The car shares a formula with the best-regarded competitors: rear-wheel drive and plenty of power. The weight distribution doesn't feel as balanced, though, and body motion isn't as well controlled as in the BMW 5 Series. The steering is numb and in no hurry to snap back to center after a turn. Overall, the car can do much of what many sport sedans can do, but it doesn't have the right feel. The Euro-firm ride is decent but not the most comfortable you'll find, even among cars with better handling. To get a softer ride, you'll have to opt for the adaptive suspension, which has three firmness settings, the lowest of which is softer than the standard suspension.
The E-Class' seats are comfortable in the best way — supportive rather than overly cushy, for the long haul — and the pictographic power controls are on the doors where every manufacturer should put them. Note that the standard upholstery is leatherette (aka vinyl) — a bummer in a luxury car. Some competitors have standard leather. The interior dimensions are competitive within the midsize luxury class, though at the lower end, with legroom that's an inch shy of the Jaguar XF's and a few tenths short of the BMW 5 Series and Lexus GS. All are rear-drive cars, which share the space-robbing high center floor hump that makes their center seat less usable. (For what it's worth, the popularity of all-wheel drive increasingly gives modern front-drive platforms, like the Audi A6's, the same problem.)
In some respects the interior is better than some competitors', in that the materials and craftsmanship are mostly high-quality, and the design is less stark than in the BMW, but there are some anomalies. The ventilation knobs have a loose and cheap feel and sound, and the pop-up plastic lock knobs are possibly the crappiest part I've ever seen in a Mercedes. Last redesigned for 2003, the E-Class is due for an update, and it shows inside. The S-Class' interior is splendid, and even the entry-level C-Class improves on aspects of the E. It was redesigned for 2008, so the next E should also leap forward.
Among the cabin's pluses were my test car's optional panoramic moonroof — essentially separate panes over the front and rear seats. The main annoyance was the center armrest, if you can call it that. It's a cupholder/storage area with a sliding lid that's not even comfortable when closed. It's not the best location for cupholders, and the storage bin is small. You can remove the cupholder module for more space, but then ... no cupholders. Storage options were otherwise decent, with a reasonably sized glove compartment and door pockets front and rear, cubbies on the fronts of the front seat cushions and seatback pockets for the backseat.
In Insurance Institute for Highway Safety crash tests, the E-Class scored Good (the highest rating) in a frontal impact and Acceptable in the side-impact test. Acceptable is acceptable, but many cars — especially luxury models — now boast Good ratings for side impact. (The BMW 5 Series hasn't been tested with optional side-impact airbags; without the feature, it scored Marginal.) Side-impact torso airbags are standard on the E-Class for the outboard rear as well as the front seats. Other airbags include side curtain bags for head protection along the side windows (front and rear) and of course the required front bags. The front seats have active head restraints.
Along with the antilock brakes with brake assist comes a standard electronic stability system with traction control. Also included is Tele Aid, Mercedes' version of GM's OnStar, and the Pre-Safe system. Pre-Safe senses emergency situations, when brake assist activates or oversteer or understeer occur, and it prepares the car for a collision by cinching the electric seat belt pretensioners and adjusting the front passenger seat to position the occupant optimally for impact.
With its 15.9-cubic-foot trunk, the E-Class is midrange for cargo volume. The Jaguar XF has 17.7 cu. ft. and the Lexus GS has 12.7 cu. ft. A 60/40-split folding backseat adds versatility, but it's a $350 option. Why do we pay more in luxury cars for features that are standard on econoboxes? At least the Audi A6 and Jaguar XF include a folding backseat as standard equipment.
As shown in the photos, the seat cushions must be flipped forward before the backrests can fold flat. The best thing you can say about this old-school approach is that it results in a flat cargo floor. Unfortunately, you have to flip the cushion from the back door, but the backrest release is in the trunk. It would be better if the backrest release were in the cabin — or if you didn't have to flip the cushion at all. A power trunk closer is a stand-alone option.
E-Class in the Market
The E-Class is definitely showing its age. The strength of the brand and relatively high resale values allow Mercedes to charge more than most of its competitors, and to nickel-and-dime buyers on some basic options like the folding backseat, leather, bi-xenon headlights, parking sonar and heated seats. At this size and price, the E-Class has a lot of competition apart from the European models I concentrated on, including the Acura TL and RL and the Cadillac CTS and STS. A choice of engines, transmissions and drivelines are becoming the norm, so this old dog will need to learn some new tricks soon if it wants to keep up with the pack.
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