You walk into a car dealership and the salesman asks if you would like to test-drive a well-equipped mid-size sedan using a new kind of technology. The vehicle gets 30 percent better fuel economy than the conventional version, is much zippier from a standstill, and is so clean that it acts like a vacuum cleaner actually removing dangerous particles of pollution from the air as you drive down city roads. You ask, “Is the vehicle some sort of new hybrid?” The salesman replies, “No. It’s a diesel!”

That’s right: Diesel. In late 2008, the first so-called “clean diesels” will become available in all 50 states by achieving the average emission level of most cars. Reaching this level of cleanliness—what the federal government calls “Tier 2, Bin 5”—requires deployment of some very fancy technology in the form of improved injection and combustion systems, and better exhaust traps and treatment systems. But that technology is just about ready to roll out. “We don’t have to ask the question over and over again whether it’s possible with a diesel to comply with Tier 2, Bin 5 emissions rules,” said Johannes-Joerg Rueger, vice president of diesel engineering at Bosch, a leading diesel technology provider. “There’s no doubt.”

Excitement When You Hit the Throttle

Rueger and other diesel experts appeared on a panel about “clean diesel” at the recent Auto FutureTech Summit in Vancouver, British Columbia. The panel moderator, Tim Johnson, director of environmental technologies, Corning Inc., said, “Diesel has a major role to play because it’s inherently more efficient than gasoline combustion. It produces about 20 percent fewer greenhouse gases, well-to-wheel, versus gasoline. And particle emissions coming out of the tailpipe are at or less than ambient.” The panel did its share of cheerleading, portraying diesel as clean, green and fun. “The core attribute of the modern diesel is torque performance, which is available to the driver at low engine speeds,” said Kevin McMahon, managing partner at the Martec Group, a market research firm. “Torque is what creates driving excitement and it’s the only thing we feel when we hit the throttle.”

But the panel didn’t sidestep the most difficult challenges facing the wider adoption of diesel vehicles in North America. Bosch predicts dramatic growth of diesel vehicles—nearly one out of every seven new vehicles purchased will be diesel by 2015. Rueger acknowledged, “There’s no silver bullet. Diesel is not the silver bullet.” He added, “And hybrid is definitely not the silver bullet either.” According to the panelists, hybrids—while slightly cleaner on smog-producing tailpipe emissions—have a higher cost of ownership and yield limited efficiency benefits in highway driving. Despite these issues, consumers view hybrids as environmental saviors and are buying hybrids in impressive numbers.

Combining diesel and hybrids, and using biofuels in diesel engines, were discussed as possibilities—but diesel-hybrids were generally viewed as too expensive, and lack of standards for biodiesel were viewed as an impediment.

Top Five Obstacles

Will clean diesel grow at the same rate as hybrids? Only if these five obstacles, identified by the panel, are overcome.

High Cost of Diesel Fuel
In March 2008, the average price of diesel fuel was nearly 70 cents higher than a gallon of regular unleaded. McMahon said, “The biggest unknown right now is the cost of diesel fuel. In North America, it’s abnormally high. If the price of diesel fuel remains extremely high relative to gasoline, I think a lot of consumer will think, that’s like jet fuel, and I’m turned off by the concept of buying that exotic fuel for my vehicle.”

Lack of Incentives for Diesel Vehicles

Consumers and automakers are offered various incentives for hybrids, plug-in hybrids, electric cars, and biofuel-powered vehicles. Those don’t exist for diesels, with the exception of CAFE credits for Biodiesel-20 capability. “The government could promote innovation and ensure fair competition by establishing technology-neutral incentive programs. Clean diesel has the advantage on reduced CO2 emissions,” said Norbert Krause, director of engineering and environmental, Volkswagen Group North America. “We have diesels cleaning the air, at least in regard to particulates, but incentives were given to hybrids or E85. But nobody is talking about incentives for clean diesel.”

Limited Availability of Diesel Fuel

Currently, diesels make up about 5 percent of the light-duty market. If diesels grow in popularity over a few decades, they could become victims of their own success by burdening the fueling infrastructure. “The refinery mix is generally a fixed entity, that is they are configured to produce a fixed amount of gasoline to a fixed amount of diesel,” said Johnson. “We’re wondering whether or not the fuel infrastructure in the United States can tolerate a 20 or 30 or 40 percent penetration of diesel.”

Long-term Limitations of the Technology

Clean diesel engine technology is ready to roll out today, but can it produce significant long-term improvements on par with plug-in hybrids, battery-electric vehicles and fuel cell cars? “The only technology currently available that can get us a step-function improvement of 25 to 30 percent fuel economy is diesel,” said Reginald Modlin, director of environmental affairs, Chrysler. “But all the regulatory drivers are driving us to 35, 40, 45 percent improvements. This great technology is merely a step into what we do for the longer term future.” Adding micro-hybrid “stop-start” technology to diesel engines could push diesel to the higher levels of efficiency.

Persistent Negative Consumer Perception

“Our highest challenge is to overcome the bad reputation of diesel as dirty and smelly,” said Rueger. “People who drive the new diesels in our test fleet literally do not believe there’s a diesel engine in there.”