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: Clean Diesel. New technology will allow clean diesels to achieve the same emissions standards as the average gasoline car.
Are diesel vehicles a viable green alternative to hybrids?
When it comes to fuel efficiency, the answer is yes. The Volkswagen Jetta Diesel, with a combined highway/city fuel rating of 35 mpg, is in the same league as the most fuel-efficient hybrids. When considering the other benefits of a diesel vehicle—like great performance and long life—modern clean diesel vehicles really give hybrids a run for their money. (Keep in mind: high fuel efficiency means low carbon emissions.)
Reaching the higher level of cleanliness 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.
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.
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