If diesels are the answer, Mercedes-Benz can't wait for the question

2007 Mercedes-Benz E320 Bluetec
On Sale: Now
Base Price: $52,325
Drivetrain: 3.0-liter, 208-hp, 400-lb-ft turbocharged diesel V6; rwd, seven-speed automatic
Curb Weight: 3860 lbs
0 To 60 Mph: 6.6 seconds
Fuel Economy (Epa Combined): 31 mpg

2007 Mercedes-Benz E320 Bluetec
We've been shown the future, and it's not bad at all.

As of now, however, the future does not apply in California or four heavily populated northeastern states. And those of us in the other 45 might reasonably ask: If this car represents the future, why aren't there more like it?

Mercedes-Benz says its E320 Bluetec sedan is the only diesel-powered, 2007-model passenger car available in the United States. Concurrent with Bluetec, Mercedes will unleash a publicity blitz intended to convince you and your neighbors that diesel is the way to go. Hear the pitch, and you might envision wildflowers sprouting from the E320's tailpipe and petroleum reserves to last till the end of time.

We say the E320 Bluetec delivers the torque of a large-displacement V8 and the fuel economy of a small-displacement four. Those who purchase the Bluetec will give up nothing consequential, compared with a gasoline-powered E350, and gain more than 30 percent in real-world fuel mileage.

The rest is up to you, your neighbors and the bureaucrats.

THE CAR

The E320 Bluetec went on sale Oct. 16, or the day after the introduction of federally mandated low-sulfur diesel. The fuel reduces sulfur from 500 parts per million to 15 ppm, and it's required to operate the low-emissions diesel in the E320.

The Bluetec is a garden-variety E-Class, equipped identically to the gasoline-powered E350 except for its 3.0-liter diesel. This 72-degree aluminum V6 has four cams, four valves per cylinder and balance shafts. It features Mercedes' third-generation common-rail direct injection, delivering fuel at 23,200 psi through—for the first time—piezo injectors. The high-tech electronic injectors supply up to five injections per stroke. More than any single component, they reduce clattering diesel noise.

Mercedes says the Bluetec V6 is lighter than its previous, inline diesel and compact enough to fit into its small C-Class sedan. In the E-Class, the engine generates 208 hp at 3800 rpm and an impressive 400 lb-ft of torque as low as 1600 rpm. For comparison, the E-Class' 3.5-liter gasoline V6 delivers peaks of 268 hp and 258 lb-ft.

Performance? Mercedes reports 0-to-60-mph times of 6.5 seconds for the E350 and 6.6 for the E320 Bluetec. If that's quick measured against our preconceptions about diesels, it's worth noting the 0.1 second may be a function of weight rather than engine. At 3860 pounds, the Bluetec weighs 120 pounds more than the E350. To launch its publicity blitz, Mercedes ran three essentially stock E320s at an average speed of 139.7 mph for 100,000 miles.

The 0-to-60-mph times don't tell the whole story, either. In short bursts, with its immediate, significant torque advantage, the E320 buries the E350. It snaps the neck out of the hole like a hot rod, and it hits 30 mph in a couple of blinks.

From the driver's seat, the only obvious difference in the Bluetec is that it shifts up sooner than the E350 at full throttle, but its 4800-rpm redline may surprise as well. You have to listen intently to distinguish the diesel's idling noise from the gasoline engine's—and that's when you're leaning into the engine bay, not sitting inside.

At $52,325, the E320 Bluetec retails for exactly $1,000 more than the E350. It delivers 26 mpg in the city and 37 mpg on the highway, according to the EPA, compared with 19/26 for the E350. The Bluetec also gets better mileage in the EPA cycle than a Mini Cooper (26/34 automatic, 28/36 manual) or a Suzuki Swift (24/34, 26/35).

PRACTICALLY GREEN

In the coming months, you will hear Mercedes-Benz tout diesels as a better alternative propulsion source than gasoline-electric hybrids. "Better" is as subjective a label as there is, but certain conclusions can be drawn.

At market prices that are likely to apply over the next few years, gasoline-electric hybrids don't make economic sense. Do the math, and it's crystal clear that a hybrid buyer cannot reasonably expect to recoup the buy-in cost of the hybrid in lower operating costs in a driving lifetime, much less five years of ownership.

The appropriate comparison here is Bluetec and the Lexus GS 450h sedan. At 15,000 miles per year, the Bluetec owner will recover that $1,000 price premium (compared with the E350) in lower fuel costs in less than two years, depending on the relative price of diesel and gasoline. Over five years, Bluetec represents a savings of $2,000 to $3,000 in fuel costs.

The 2007 GS 450h retails at $54,900 and delivers 25 mpg in the city, 28 on the highway, according to the EPA. The GS 350 with the same gasoline V6, retails at $44,150, with 21/29 mpg. Separate additional non-hybrid standard equipment, and the hybrid still costs about $8,500 more. Driven 60 percent city, 40 percent highway, the fuel savings with the GS 450h are negligible—less than $100 per year, and less still with a higher share of highway driving. Even with the tax incentives offered on hybrids, it would take more than 50 years to recover that $8,500.

Ultimately, a gasoline-electric hybrid is a statement of values more than a practical improvement. It may be a weaker statement than a diesel (or diesel-electric hybrid), whether or not environmentalists see it.

"You can have a hybrid for about the same cost as a clean diesel," a Sierra Club official told AutoWeek ("The Thing Before the Next Big Thing," Dec. 23, 2002). "I think it's better to skip the 19th century technology and go right to the 21st century."

Clearly, you can't have a hybrid for about the same cost. And strictly from an environmental standpoint, measured by reducing greenhouse gases such as CO2—not to mention other political hot buttons such as reliance on Middle Eastern oil—diesels may be the way to go. The simplest, best way to reduce emissions is to reduce the amount of hydrocarbons burned. The E320 Bluetec will burn less petroleum over its useful life than the GS 450h, and independent tests suggest the same applies in diesel vs. gas-electric hybrids in compact cars, SUVs and the rest.

Moreover, diesels are more readily suited to CO2-neutral biofuels, and the auto industry can build more diesels much sooner than it can build hybrids. In 2007, the capacity to build diesels will exceed that to build hybrids by a factor of 20.

BLUETEC

The above analysis holds only if the diesel is as clean as the gasoline V6 in the GS 450h. While Mercedes claims Bluetec is the cleanest diesel in the world, it's not as clean as the Lexus engine, which is behind why roughly 20 percent of U.S. drivers will not be able to buy a Bluetec.

For 2007, federal emissions requirements get more stringent, moving from the Tier 2 Bin 10 standard to Bin 8. The reduction is primarily in the two things diesel combustion produces in greater quantity than gasoline combustion: particulates such as sulfur and oxides of nitrogen, or NOx. The Bluetec easily achieves Bin 8. But five states have even tougher emissions standards.

Bluetec is a brand name for the modular emissions controls used on Mercedes' new diesel (BLUEsky, highTEC). The system uses three catalytic converters, including one formulated expressly for NOx emissions, and a particulate filter. The filter may be the most innovative component.

Critics—those who insisted that diesels would never meet stringent emissions requirements—most frequently cited particulate traps as the problem. They would have to be emptied in some fashion and could never last 100,000 miles or beyond. The Mercedes filter cleans itself every 600 miles with a thermal reaction, or an upward spike in exhaust gas temperature, that vaporizes the stored particulates. The spike is generated by a brief restriction of inlet air, retarded combustion and other upstream adjustments. When Mercedes engineers completed the E320's 100,000-mile high-speed run, they drove the cars from Laredo, Texas, to an emissions lab in Tallahassee, Florida (on one tank of fuel), where the particulate filters were certified as effective as when they were installed.

The problem for Mercedes is that California, Maine, Massachusetts, New York and Vermont have already tightened emissions another notch, to EPA Bin 5. Bin 5, which applies nationally for 2009, is identical to Bin 8 except that it cuts NOx an additional 65 percent and particulates 50 percent. No problem as far as tailpipe measurement goes, says Joachim Schommers, Mercedes' director of diesel development. Bluetec is there in particulates, and it can achieve the NOx levels with AdBlue.

AdBlue is Mercedes' brand name for urea, which, in systems developed by several manufacturers, can nearly eliminate NOx. Trace amounts of urea are injected into the exhaust stream after the particulate filter, releasing ammonia in the last catalyst and turning NOx into nitrogen and water vapor. Urea is a stable, inexpensive liquid that could be replenished like washer fluid. The system uses roughly four ounces per 100 miles, and the reservoir could be large enough that it might be refilled at each oil change.

But it will have to be refilled. If the urea reservoir ran dry, the car would not be emissions compliant. The EPA has approved urea injection in principal, but it has not decided on a mechanism to ensure that drivers refill the tank. So far, ideas range from full vehicle immobilization to one or two free starts on an empty urea tank.

While the regulators mull, consumers can choose one diesel-powered sedan—unless they live in California, Maine, Massachusetts, New York or Vermont.

POTENTIAL

Diesel fuel is still stickier and smellier than gasoline, and the odor clings more readily. If diesel cars become more prevalent in the United States, the proverbial soccer mom will have to fill them. More significant is the needed adjustment to the infrastructure. As few as 20 percent of fuel retail stations sell diesel, and adding diesel is no small challenge. It means dropping a grade of gasoline or installing more tanks, which is a difficult proposition.

The potential benefit is significant, as Western Europeans can attest. With fuel prices exceeding $6 per gallon, diesel sales have surpassed 50 percent of the new-car market. In the States, the Department of Transportation released a study in 2004 suggesting that if one-third of the light trucks on the road were diesel powered, oil consumption would decrease by 1.5 million barrels a day—roughly equal to imports from Saudi Arabia. The windfall would accrue to consumers.

Mercedes-Benz can't wait to save you some cash.

You may e-mail J.P. Vettraino at autonews@crain.com

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