In Europe, roughly half of all passenger cars sold come with fuel-efficient diesel engines.
But for a variety of reasons, passenger diesels haven't caught on in the States, though the number is climbing slowly.
Audi, proud of its diesel engine technology--which, among other things, has won the prestrigious 24 Heures du Mans endurance race in the Audi R15 TDI--is forging ahead and plans to offer a diesel variant of every model it sells in the U.S. by 2015.
Audi R15 TDI diesel race car at Petit Le Mans, Road Atlanta, October 2010
Modern clean diesels usually deliver fuel economy one-third to one-fifth better than that of a gasoline engine of similar power. They're also appealing to drive, due to their copious low-end torque. And it's often impossible to tell from behind the wheel that there's a diesel under the hood.
Currently, Audi offers diesels in just two models: the A3 TDI compact hatchback and the Q7 TDI large sport-utility vehicle. Neither model represents a large portion of its total U.S. sales, but Audi says it could sell more of the diesel variants if it could keep them in stock. Diesels represent half of A3 sales and close to 40 percent of Q7 sales this year.
Audi of America president Johan de Nysschen told industry trade journal Automotive News that it plans to add diesel versions of its current A6 midsize sedan and A8 large luxury sedan, as well as its Q5 crossover.
diesel and AdBlue fillers in Audi Q7 TDI
Its highest volume model, the A4 sports sedan, will be offered with a four-cylinder diesel when it is redesigned for the 2015 model year. The company had considered using its diesel V-6, but that engine is simply too expensive for the U.S. market, so the company expects to fit a powerful four instead.
Audi says its customers are ordering diesels at higher-than-expected rates, and that it is responding as much as to dealer demand as to the tightening fuel-economy rules. Roughly 5 percent of its sales this year represent clean diesels; de Nysschen said that number could be as high as 20 percent by 2015.
The company is also hedging its bets, adopting the Volkswagen Group hybrid-electric powertrain for a future version of its Q5 sport utility. But among Volkswagen, Porsche, and Audi--the three brands that will offer hybrids--Audi is the last, and it seemingly remains the most bullish of the three on the potential for clean diesels to save fuel.
While Audi will take a tentative step with hybrids, de Nysschen has gained some notoriety for his dismissal of electric-drive as a way to increase fuel economy. Last fall, he famously said that anyone who bought a 2011 Chevrolet Volt range-extended electric car was "an idiot."
[Automotive News (subscription required)]