Though cars and trucks running on diesel fuel remain a relatively small percentage of new cars and trucks sold in the U.S., increasing sales of such vehicles by German car companies in the U.S. points to a potentially rosier future.
And the continued success of diesels at LeMans keeps bringing attention back to the powerful fuel. Audi has won LeMans with diesel engines every year since 2006 except 2009, when Puegot won with a diesel-fueled sports car.
Audi presently sells two diesel vehicles to consumers in the U.S. -- the A3 TDI and Q7 TDI. In the next two years, though, it is expected to introduce three more -- diesel versions of the A6, A8 and Q5.
Audi is part of the Volkswagen Group, which is the top seller of diesel vehicles in the world. Volkswagen is the top seller of diesel passenger vehicles in the U.S.
"We are making a lot of headway in educating U.S. car buyers about clean diesel," says Jonathan Browning, CEO of Volkswagen of America. Volkswagen said 22% of its total U.S. sales, or 56,500, in 2010 were clean diesel "TDI" vehicles. When the company launches its new redesigned Passat family sedan in the Fall, it projects that as many as 40%, or about 50,000 it plans to build in 2012, could be run on diesel.
View Gallery: Clean Diesel Cars
What you need to know about "clean diesel"
Diesel was re-named "clean diesel" a few years ago when the standards for diesel fuel changed to contain "low sulfur." That change in the fuel, plus on-board systems that capture a lot of the tailpipe particulates, means that burning diesel fuel in a state-of-the-art passenger car or pickup truck is a lot cleaner than, say, burning the fuel in a tractor-trailer truck that doesn't have the same on board systems.
Fuel economy advantages vary with diesel passenger vehicles from 20% to about 30%. For example, the VW Jetta TDI (diesel) gets 30 mpg city/42 mpg highway for a combined 34 mpg, while the gas version (automatic transmission) of the same car gets 24 mpg city/31 highway for a combined 27 mpg. The TDI is 26% more fuel efficient. But if a driver logs a lot more highway miles than suburban commuting, the diesel's highway mileage gives them a 35% gain.
The arithmetic for judging if a diesel is for you, though, is a bit more complicated. First, a Jetta TDI with an auto/manual transmission stickers at about $24,095 without extra features and destination charges. A comparable gas version costs $20,645 before you add features and the destination charges.
Then, there is the cost of diesel fuel. The cost of diesel is usually, but not always, more than unleaded regular gas. Nationally, the week of June 13, the average cost of clean diesel was $3.95 per gallon, compared with $3.71 for unleaded gas. That's a differential of 24 cents per gallon.
There are regional differences too. In Eastern states, during the same week, the average price of diesel was 27 cents more per gallon. In the Midwest, the average spread was just 18 cents. The spread can be substantial within even one town, so it pays to shop around. In Ann Arbor, Mich., for example, diesel prices ranged this week between $4.05 and $4.25 depending on the outlet.
Price and cost, of course, are not the only considerations. Diesel engines provide great low-end torque, meaning the engine delivers great power and acceleration at low revolutions. Punch the gas pedal on most diesel cars, which are usually small displacement engines (Volkswagen Jetta is a 2.0 liter engine), and the driver can feel acceleration more appropriate to at least a V6 engine.
Part of the reason that Audi has been unbeatable at LeMans in recent years with its TDI engine is that it doesn't have to stop as many times as its petrol-powered rivals for re-fueling. That advantage translates to Audi's and Volkswagen's street vehicles. The new VW Passat has a potential driving range of almost 800 miles if you are on the highway.
More diesels coming to a showroom near you
Besides the VW Jetta, the other diesel powered vehicles for sale today include: VW Jetta Sportwagen TDI, VW Touareg TDI, Volkswagen Golf TDI, BMW 335d, Mercedes-Benz E350 Bluetec, BMW X5 xDrive35d, Mercedes-Benz ML350 Bluetec 4matic, Mercedes-Benz R350 Bluetec 4matic, Audi Q7 TDI, Audi A3 TDI, Mercedes-Benz GL350 Bluetec.
The Germans are spending big money to try and drive diesel awareness and acceptance. BMW last February spent almost $3 million to advertise its diesel in the Super Bowl. In 2010, Audi advertised its diesel vehicles in the Super Bowl and launched a broad campaign to drive interest in diesel overall. The theme: "Diesel is no longer a dirty word."
Mazda intends to be the first Asian automaker to sell a diesel powered passenger car when the company rolls out a diesel-powered vehicle in 2013, probably a version of an all-new small sport utility, the CX-5.
Honda at one point said it planned to launch diesel vehicles in the U.S., but backed off the plan after the collapse of the financial markets in 2008 and 2009. But Mazda says it is committed. "We are all in on diesel for the U.S.," says Mazda North America spokesman Jeremy Barnes. "We think there is a growing market for diesel in the U.S."
What gives many manufacturers the desire to launch diesel in the U.S. is that they sell them in great abundance in Europe. Because the European Union countries tax petrol higher than diesel, and petrol often tops $8.00 a gallon, smaller, diesel-powered vehicles are popular, representing more than half of all new vehicle sales on the continent.
That kind of tax policy that would favor diesel is not likely to be forthcoming in the U.S. where politicians are more favorably disposed to hybrid and electric vehicles. "It can be very difficult to get a member of Congress to turn out for a photo-opp for a clean diesel vehicle," Audi of America chief Johan de Nysschen told AOL Autos earlier this year.
But that bias away from diesel vehicles by policy-makers has created what many analysts call hybrid folly. What does that mean? Big SUVs like the Volkswagen Touareg and Chrysler Aspen come in gas-electric hybrid versions. But they are not well-suited to that technology. The heavier the vehicle, the less appropriate battery power becomes. Trucks and SUVs are much better suited to diesel, which has long been applied to Super Duty and Heavy Duty pickup trucks at Ford, GM and Dodge. Accordingly, hybrid versions of SUVs and truck have been slow sellers.
Audi has won the 24 Hours of LeMans five of the last six years with its TDI diesel race car. The year it lost, 2009, to Peugeot, the French automaker also won with a diesel car. Diesel engines have transformed the race completely to the point where non-diesels will have a terrible time competing at all in the future for the top award.
It may take a lot more wins, and much higher gas prices, though, before diesel cars get as good a public relations image as hybrids.