A Guide to Diesel & Clean Diesel Cars

What Is A Diesel Vehicle?

A diesel vehicle uses an engine that has a different combustion cycle than a gasoline engine. In a gasoline engine, fuel is mixed with air, drawn into the cylinder, and ignited by a 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 diesels achieve roughly 50 percent higher fuel economy than their gasoline counterparts.

In Oct. 2008, Audi held a 4,800-mile American driving tour to promote the carmaker’s TDI (turbocharged direct injection) clean-diesel technology. Audi's TDIs are powerful, very efficient, and pass California's strict emissions standards. The Audi Q7 TDI will be introduced in the US in early 2009.

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 diesels achieve roughly 50 percent higher fuel economy than their gasoline counterparts.

Diesel vehicles now account for nearly half of all new vehicle sales in Europe. In some European countries, such as France, diesel vehicles account for as much as 70 percent of new car sales. Diesels represent about 3 percent of today’s new car market. J.D. Power, a market research firm, predicts that diesel will rise to 11.5 percent by 2015—rising at a higher rate and to a higher level than gas-electric hybrids. Mercedes, Volkswagen, and Chrysler are the key players in the diesel market

Diesel Benefits

1. Higher fuel economy
2. Diesel engines last longer, and fetch higher resale values
3. Diesel engines can be run on biofuel (biodiesel)
4. Diesels provide greater torque; great for rapid acceleration and towing
5. Driving range on a tank is longer

Diesel Drawbacks

1. Diesel fuel is more expensive in the US (In Europe, it’s taxed less heavily.)
2. Few models are available with a diesel engine
3. Particulate matter and NOx emissions are higher
4. Diesel vehicles are usually more expensive, although “clean diesel” carries purchase incentives
5. Diesel availability is more limited; there are fewer diesel pumps