Diesel, Dirty No More


  • 2006 VW Jetta - Rear

    2006 VW Jetta - Rear

    Equipped with an automatic transmission, Volkswagen's 2006 Jetta TDI sedan gets 35 mpg city/42 mpg highway compared to the base gasoline engine's 22/30 EPA rating. | March 18, 2010

5 Photos

Diesel, once long ignored like the ugly stepchild of the fossil fuel family, has worked its way out of the dirty dungeon and made it to the ball. As in the Cinderella fairy tale, diesel's fairy godmothers, the auto industry and oil companies, have transformed it from a grimy, smelly mess into a serious contender for Prince Charming's hand. More importantly, fuel-efficient diesel vehicles are now serious contenders for Americans' garages, as buyers seek out the most painless solutions to high gas prices that aren't going down anytime soon.

The change from social outcast to debutante was not an easy one, but diesel may soon have many American suitors. Why? Today's diesel engines provide 20-to-40-percent better fuel economy and offer more torque at lower rpm when compared to their gasoline counterparts. Diesel engines are also substantially less harmful to the environment today than they were in the past — and are headed down the road to becoming even cleaner in the near future. While some automakers don't have plans to offer diesels in light-duty passenger vehicles just yet, all of the major manufacturers are taking a serious look at the technology.

Why Diesel? There's a powerful impetus for the government to encourage diesel-powered vehicles in the United States: It would reduce our dependence on foreign oil. Of all the types of internal-combustion engines, the diesel engine is the most efficient: A given amount of diesel fuel can make more power than the same amount of gasoline. (For an overview on the diesel engine, read How Hybrids and Diesels Work.)

According to the Department of Energy, if 30 percent of the passenger cars and light-duty trucks in the U.S. had diesel engines, U.S. net crude oil imports would be reduced by 350,000 barrels per day. To put this in context, U.S. crude imports averaged well over 20 million barrels a day in the first half of 2005, according to the Energy Information Administration, a statistical agency within the Department of Energy, so diesel is only one piece of a more comprehensive solution to oil dependency.

The difficulty is in building diesel-powered vehicles that meet the emissions standards nationwide at a price that consumers are willing to pay. Much like hybrids, diesels require automakers to develop and implement more sophisticated technology to achieve emissions gains. This of course adds cost, which gets passed on to the consumer. On the plus side, Congress passed energy legislation in July 2005 that will give buyers of clean diesel vehicles tax credits of up to $3,400 — an incentive designed to offset the increased cost of diesel technology in much the same way as the tax credits for hybrid vehicles.

Americans' interest in buying diesel-powered vehicles is on the rise. It's a popular topic in the Edmunds.com forums and the rising cost of gasoline makes diesel even more attractive. According to research by J.D. Power and Associates, the number of diesel-powered vehicles purchased by U.S. consumers will more than double by 2012.

Many U.S. consumers are already speaking with their wallets by purchasing light-duty diesel-powered vehicles, but you can only buy them new in 45 states. Currently, no light-duty diesel-powered vehicles are sold new in California, Maine, Massachusetts, New York or Vermont because of stricter emissions standards in those states. (Diesel-powered trucks, such as the heavy-duty versions of the Chevrolet Silverado/GMC Sierra, Dodge Ram and Ford F-Series, fall under different emissions rules and they are permitted.)

Some In, Some Out Between state restrictions on sales and tightening emissions standards (which will become even more stringent in 2007), many automakers have opted to stay out of the diesel market in the U.S. Still, others are pressing ahead. Volkswagen is moving forward with its diesel program, hedging its bets that the technology will be in place by the time the stricter standards take effect. DaimlerChrysler is also taking this route with its Jeep and Mercedes-Benz divisions.

Volkswagen has long been a proponent of diesel technology and currently offers diesel versions of its New Beetle, Golf and Jetta in the U.S. A diesel V10 version of VW's Touareg SUV was on the market for a short time, but was then removed by Volkswagen because of a change in an emissions rule. It is slated to return to the U.S. market in early 2006.

The diesel version of the Mercedes-Benz E-Class sedan, introduced in the U.S. in 2004, meets 45-state emissions standards. By eliminating sales in the five states with stricter standards, Mercedes-Benz is effectively reducing its sales potential by 40 percent. Yet the company has sold nearly one-third more E320 CDI vehicles than its initial annual projections, proving that diesels can be a hit with the public even when the two largest markets, California and New York, are not in play. Mercedes-Benz has said it will most likely offer diesel versions of its M-Class, G-Class and R-Class models in the U.S. in the future, though no firm dates have been set. The possibility of a diesel version of its S-Class is under consideration.

"It's our longer-term goal to make our diesel models available in all 50 states and, if the fuel suppliers are able to get the cleaner fuel, we are confident we can build diesel vehicles that will meet the future emissions standards," said Mercedes-Benz spokesperson Rob Moran.

The diesel version of the Jeep Liberty has also proved popular with buyers. Jeep is projecting sales of 10,000 Liberty CRD models for the 2005 calendar year — double what it originally projected. It's not a surprise when you consider that fuel economy is 22-percent better than in a comparably equipped gasoline Liberty, in addition to improvements in towing capacity and driving range. Jeep has added another 2,500 vehicles to its production schedule to meet the demand and the company is still unsure if that will suffice. Jeep is so encouraged by Liberty sales that it is assessing whether to adapt the powertrain to other vehicles.

Future Standards, Big Challenges While the current emissions standards are different for diesel vehicles compared to gasoline engines, the new federal standards, which go into effect in 2007, require diesel-powered vehicles to meet the same pollution levels as gasoline models. In some areas, such as carbon-dioxide emissions, diesels are actually more environmentally friendly than gasoline, but pollutants such as nitrogen oxide and soot are a different story altogether. On average, the new standards would mean a 77-percent cut in nitrogen-oxide emissions and an 88-percent drop in particulate emissions to put diesels on an equal playing field with gasoline cars.

The big challenge is that the emissions control systems, which filter out nitrogen oxides and particulates, don't work well with today's U.S. diesel fuel, because our diesel fuel has a much higher sulfur content than Europe's. The EPA has mandated diesel fuel to be produced with lower sulfur content, but that change won't take full effect until 2006 and even then the fuel won't be comparable to Europe's fuel.

Several alternatives are being discussed about the best way to reduce emissions to meet future standards. One possibility is a system that would require a person to use an additive akin to adding windshield washer fluid. There's a concern, however, that owners won't add it regularly because there will be no noticeable difference in the vehicle without it — it simply won't be emissions-compliant. Another option is to use a component to trap the particulate matter, but these systems need to rid themselves of the matter somehow in order to be effective. Delphi has developed a fuel reformer that may provide a solution to this problem, but further testing is necessary.

At issue with creating a diesel engine that meets the stricter emissions standards of the future is the long-term durability of the emissions control equipment. Toyota is one of several major automakers taking a conservative approach in the U.S., despite the fact that diesel-powered vehicles represent over 30 percent of its sales in Europe. "We're not there yet," said Mike Love, national regulatory affairs manager at Toyota. "We are not confident that we can meet standards for the useful life of the engine." Toyota, which is known for the longevity of its vehicles, notes that as the systems wear to 100,000 miles and beyond, they are no longer effective at meeting the emissions standards.

Wait-and-See Approach Other automakers that currently offer diesels in other countries feel they could modify them to meet the tightened U.S. standards, but are concerned about adding too much cost to the vehicle. "We believe we can meet the new emissions standards, but it is questionable if it is feasible at a price point that makes it desirable to the customer," said GM spokesperson Nick Richards.

Ford, which is currently testing a diesel-powered Focus for the U.S. market, is undecided about whether to bring it to America within the next five years. "We want to make sure we can meet the new standards before we consider bringing it to market," Dick Baker, corporate technical specialist for Ford's Advanced Diesel Systems group, said.

Even BMW, which has succeeded in building diesel versions of nearly every model it manufactures for the European market has no plans to bring a diesel car to America. "If we could offer a 50-state clean diesel-powered car, the likelihood [of bringing it to America] would certainly be greater," BMW Product Communications Manager Dave Buchko said.

Shedding the Dirty Image Even with the pressures of higher gas prices, one of the biggest hurdles for diesel to overcome is its reputation with the American consumer. Baby boomers are likely to remember the fuel crises of the 1970s and the failed attempt by General Motors to offer diesel drivetrains. Oh sure, the various diesel-powered Cadillacs started and ran…technically. But few consumers wanted to actually drive one. Others are likely to think of noisy, smelly, smoke-belching buses and large trucks that are still seen on the streets today. Still more may remember plugging in their diesels on cold winter nights only to find them hard to start in the morning. Today's diesel technology is none of these things.

Let's take the 2006 Volkswagen Jetta TDI sedan with an automatic transmission as an example. Despite the fact that the diesel four-cylinder version has 50 less horsepower, it has more torque, especially at the all-important low-end: 177 lb-ft at a low 1,800 rpm versus 170 lb-ft at a higher 3,750 rpm in the base 2.5-liter, five-cylinder gasoline engine. What this means is that the TDI Jettas are likely to feel a tad quicker off the line than 2.5-equipped counterparts. More importantly, fuel economy is significantly improved: the diesel version is rated at 35 mpg city/42 mpg highway compared to just 22 city/30 highway with the gasoline model.

Opening Minds The advances in diesel technology have opened the minds of many who were unsure that diesel could ever be an environmentally friendly alternative. Dr. Alan Lloyd is chairman of the California Air Resources Board (CARB), which is responsible for California's strict emissions standards. He noted that the auto industry is making greater advances toward cleaner diesel engines and that he would welcome sales of diesel vehicles in the state in the future, assuming they met gasoline passenger-car emissions standards.

Leon G. Billings, president of Clean Air Trust, describes meeting the new standards as a "tall order," but he is still hopeful. "The key to diesel technology for tomorrow's cars, SUVs and pickups is likely to be the availability of really clean fuel. Once the makers of emissions control technology are assured a sulfur-free fuel supply, they will be able to provide systems which will achieve standards for gasoline-powered vehicles."

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