Diesel Efficiency
Diesel-powered passenger vehicles are another fuel-efficient option.
Popular in Europe, diesel models are limited in their availability in the U.S. because five states—California, New York, Massachusetts, Maine and Vermont—prohibit their sale due to emission restrictions. Note that in contrast, gas-electric hybrid vehicles are sold in all states. Indeed, hybrids are far cleaner in many emission properties than even conventional gasoline vehicles.
Still, diesels are known for getting extra mileage out of every gallon of fuel. They offer better torque than many gasoline engines. And their price differential over gasoline models generally is much smaller than that for hybrids.
For example, Mercedes-Benz's midsize 2007 E320 diesel sedan has a starting MSRP of $51,550, which is only $1,000 more than the starting price for a 2007 E350 gasoline sedan.
Yet the 3.0-liter V6 in the E320 BLUETEC sedan, as the diesel version is called, puts out an amazing 388 lb-ft of torque starting as low as 1600 rpm and compares with the 258 lb-ft of torque starting at 2400 rpm in the 3.5-liter V6 gasoline engine in the E350 sedan.
The diesel E-Class's fuel economy rating is 26/35 mpg, for a combined 30 mpg, and compares with 19/26, for a combined 21 mpg, in the gasoline E350.
Thus, if drivers maximized the diesel's fuel economy and got the 9 extra miles per gallon, it would take less three years to recoup the approximately $1,000 extra cost for the diesel engine in the E-Class if diesel prices were in the neighborhood of $2.40 a gallon.
Other Diesel Matters
Diesel engines are getting cleaner. Thanks to cleaner diesel fuel with lower sulfur content now available in the U.S. and new vehicle technology that filters or traps troubling engine particulate emissions, diesels are becoming cleaner than ever.
In fact, Mercedes touts its Bluetec as the "cleanest diesel in the world" and has joined with Audi, Volkswagen and DaimlerChrysler's Chrysler Group to spread the Bluetec name across other diesel models in the coming years.
Some consumers, however, will object to having a diesel because these cars typically—though not always—are noisier than gasoline-powered vehicles. Some buyers also might object to the telltale odor that is associated with diesel vehicles.
And, not every urban filling station has a diesel pump. In some cases, drivers might need to venture farther from suburban neighborhoods to locate a place to fill up.
Nonetheless, diesel engines have been with us for a long time—the first diesel-powered passenger car was a 1936 Mercedes—and diesel engines are known for their durability. Hence, they're standard fare under the hoods of big semi-trucks.