You walk into a car dealership and the salesman asks if you would like to test-drive a well-equipped, technologically advanced midsize sedan. The vehicle gets 30 percent better fuel economy than the conventional version, is much zippier, and runs so clean that it actually removes dangerous particles of pollution from the air as you drive down city streets. You ask, "Is the vehicle some sort of new hybrid?" The salesman replies, "No. It's a diesel!"
That's right: Diesel. New technology will allow so-called "clean diesels" to achieve the same emissions standards as the average gasoline car—and thus earn entry into all 50 states. Currently, California and other states following California emissions laws don't allow new diesels to be sold.
Reaching the higher level of cleanliness—what the federal government calls "Tier 2, Bin 5"—requires deployment of some very fancy technologies such as improved injection and combustion systems, and better exhaust traps and treatment systems. The filter systems will, in fact, emit exhaust with fewer particulates than it takes in. "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."
What Is Diesel?
Diesels are also known as compression ignition engines, and have a different combustion cycle than gasoline engines.
- In a gasoline engine, fuel is mixed with air, drawn into the cylinder, and ignited by a spark from the spark plug.
- In a diesel, air is drawn into the cylinder and compressed first without fuel present. This compression heats the air to such a high temperature that when fuel is then injected into the cylinder, it combusts.
By using higher compression ratios and higher combustion temperatures, diesels operate more efficiently. As a result, diesel vehicles attain better fuel economy than their gasoline counterparts. This fuel economy advantage is enhanced by the fact that a gallon of diesel fuel contains about 10 percent more energy than a gallon of gasoline. These two factors help modern direct-injection diesel vehicles achieve roughly 30 to 50 percent higher fuel economy than their gasoline-fueled counterparts.
Clean Diesel Means Reduced Emissions
Modern diesels require something of an environmental tradeoff. While generating fewer greenhouse gas emissions—due to greater fuel efficiency—diesels emit larger amounts of particulate matter and oxides that contribute to smog.
Clean diesel technology will almost completely eliminate those problems. Mercedes-Benz uses the brand name "Bluetec" for its clean diesel technology, which will be applied to a range of sedans, SUVs, and wagons. But that's only the beginning. Car buyers looking for speedy acceleration and good fuel economy will soon enjoy choices from several carmakers, most notably Volkswagen, Chrysler, and Honda.
Some industry analysts expect diesels to become more popular than hybrids, but a number of obstacles might prevent that from happening. First, American drivers will need to give diesels a try, despite a persistent misperception that diesels are dirty, smelly, and noisy. But the biggest challenge could be the rising cost of diesel fuel. Throughout 2008, the average price of diesel fuel was nearly 70 cents higher than a gallon of regular unleaded gasoline.
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