Clean Diesel: What You Need to Know

Car gasoline tank, Diesel only
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Americans have funny ideas about diesel cars, which have prevented us from diving too deeply into this ancient (as old as the gas engine) but increasingly environmentally friendly technology. Could that be changing? At the German-American Chamber of Commerce’s “Clean Diesel on the Rise” forum in New York last week, automakers pointed out that younger car buyers weren’t even alive when the cacophonous, smelly, and slow diesels of the 70s and 80s were stinking up the alternative tech’s reputation.

The bottom line is that diesels today are 20 percent more fuel efficient than comparable gas cars, and are no worse in terms of emissions and performance. They’re not even particularly noisy. I just drove BMW’s new 328d diesel (that's it below) in New Jersey, which delivers 45 mpg on the highway and, well, it was a BMW. Acceleration was comparable to a gas version, and only a hint of that distinctive diesel engine note was detectable. BMW has a new three-cylinder engine, and I’m fascinated to see what it will be able to deliver in its anticipated diesel version.

Diesels today run on low-sulfur fuel that’s among the cleanest in the world, and greenhouse gas, nitrogen oxide (NOX) and particulate emissions are way down. Reports the Diesel Technology Forum, “Emissions from today’s diesel trucks and buses are near zero thanks to more efficient engines, more effective emissions control technology and the nationwide availability of ultra-low sulfur diesel fuel.” Greyhound just ordered 220 clean diesel buses that cut particulate matter and NOX by 98 percent.

So we have good reason to love or at least like diesels, but we don’t—at least not like Europeans do. In the U.S., only 2.6 percent of cars on the road are diesel-powered, compared to 55 percent in Europe. There are reasons for that, some of them based on misperceptions.

Volkswagen (which had 70 percent of the U.S. market with its TDI diesels in 2012) just released its Clean Diesel IQ survey, which finds opinion changing for the better, but a third of gasoline and hybrid drivers “believe that clean diesel vehicles are noisy and smell bad.” VW sees this as a “time warp” effect. Older diesels couldn’t get out of their own way, and put out clouds of evil black smoke—some people remember that. Some 36 percent of gasoline drivers in VW’s survey say diesels ‘smell terrible.”

The people who actually own today’s clean diesels know better. An impressive 94 percent of current diesel owners would consider buying another one, but only 26 percent of gas and hybrid drivers are willing to think about it. Those with the most open minds are males aged 35-54, with a college degree or higher. The cars are getting more performance oriented and sexier. That's the Audi SQ5, with more than 300 horsepower, below.

John Voelcker, editor of and moderator of the “Clean Diesel on the Rise” panel, said all of the participants were confident that the new clean-diesel cars would take a larger share of the market than they have over the last couple of decades.

Voelcker noted that owners of Volkswagen Jetta TDI cars routinely report getting more miles per gallon of diesel fuel than the car's EPA rating, especially in high-speed highway use, when diesels run most efficiently.

But agreement among the different companies wasn't universal on the relative strengths and weaknesses of diesels, hybrids, and plug-in electric cars, he said. A few panelists all but sneered at hybrids for their driving qualities, even more so at plug-in electric cars—variously calling them “city cars” and “green darlings”—and suggesting that the diesels’ superior torque made the driving experience simply unparalleled.

Other panelists tended more toward the consensus among industry analysts, which is that all three technologies will find adherents in the market, as long-distance drivers opt for diesels while those looking for commuter cars or around-town vehicles tend toward the much lower running costs of hybrids and plug-ins.

What’s the long-term outlook for diesels 10 years out—when emissions regulations become far more stringent than they are now? Nobody’s sure, though the consensus was that “the diesel engine is here to stay.”

The biggest knock on diesels today is the price of the fuel. As I write, AAA tells me that regular gasoline averages $3.63 nationally, and diesel $4. That’s better than it was—the price averaged $4.16 a year ago. I remember diesel being cheaper than gas, but it’s been the other way around since 2004, the Department of Energy tells me.

Why? According to the Energy Information Agency:

  • High worldwide demand for diesel fuel and other distillate fuel oils, especially in Europe, China, India, and the United States, and relatively limited refining capacity.
  • The transition to less polluting, lower-sulfur diesel fuels in the United States affected diesel fuel production and distribution costs.
  • The Federal excise tax for on-highway diesel fuel of 24.4 cents/gallon is six cents per gallon higher the gasoline tax.

Still, the fuel efficiency advantage overcomes the price disadvantage in most cases. Do the math. Consider a clean diesel. All those Europeans can’t be wrong!