In the April 2008 issue we published a story called "Fuel for Thought" that addressed the European diesel revolution coming to the United States. We gave you a peek at and offered speculation on some of the platforms likely to make the Transatlantic voyage for use on public roads here in America. Though still in its early stages, the revolution is now in full swing, spearheaded by four major German manufacturers. Here's the current state of affairs as we see it.

R8 Le Mans
Don't get too excited-Audi has no concrete plans to build a production version of the R8 Le Mans, equipped with a V12 TDI producing a maximum 1,000 Nm of torque (about 740 lb-ft). Initially, designers had problems fitting a gearbox that could stand up to such a massive amount of twist, and the entire powertrain package proved a problematic fit in the existing R8 rear end. Reportedly, the concept vehicle is a completely new animal from the doors back, and building a road-going car to this spec could drive production costs into impossibility. But that doesn't mean Audi can't or won't build a high-performance diesel version of the car. A diesel-powered super sports car, especially one drawn so directly from Audi's legendary motorsports heritage, could go a long way in selling diesel technology to the unconverted masses.

In contrast to Volkswagen of America, Audi USA may at first seem somewhat indifferent to the diesel revolution even though Audi AG is regarded by many as the world's leading diesel innovator. The company has promoted diesel technology with international motorsports programs and cross-country road events promoting the efficiency and reliability of the technology, but currently only has plans to sell the Q7 SUV with a 3.0-liter TDI engine. Sure, a Q7 with a TDI is what's needed to keep SUV sales moving, but you'd think that with the current demand for smaller, high-mileage vehicles something like a 46-mpg A3 would drive sales sky high. In Europe you're able to buy the A5 with a 3.0-liter TDI. Compare that to a U.S.-spec 3.2-liter gas engine (both are equipped with a six-speed manual transmission):

*A5 3.0 TDI Quattro
(European-spec): 240 hp @ 4000 rpm, 368 lb-ft @ 1500 rpm0-62 mph in 5.9 sec., 35 mpg (combined cycle)

*A5 3.2 Quattro
(U.S.-spec, gasoline): 265 hp @ 6500 rpm, 243 lb-ft @ 3000 rpm0-60 mph in 5.8 sec., 22 mpg (combined cycle)Based solely on the numbers, the choice seems obvious. The A5 3.0 TDI is as fast to 60 mph but gives a combined mpg increase of approximately 60 percent. Clearly, Audi has the tools and know-how to create some amazing diesel products, and it could be that we'll see further products come to the States in the future. But for now, Audi brass just isn't saying.

Current Model:
Q7 3.0 TDI
Engine: 3.0-liter V6, turbocharged, direct injection
Output: 221 hp @ 4000 rpm, 405 lb-ft @ 2000 rpm
Efficiency: 19/25 mpg

Until recently, BMW never surprised anyone with its U.S.-bound vehicle/engine combos. Always predictable, it never really strayed, always building the same naturally aspirated engines, each generation more refined and with a bit more power. That was until, out of left field, the company announced it would be getting back into the turbo business, shortly after releasing the 3.0-liter N54 twin-turbo gasoline engine. BMW kept the surprises coming, shocking me with an even-more-ultimate driving machine equipped with a 50-state-legal, 3.0-liter twin-turbo engine with 265 hp and 425 lb-ft of torque that could propel a 3 Series sedan from zero to 60 mph in just 6 seconds. If you take a quick look at BMW's European heritage you can see that the company has actually been developing and refining diesel technology for more than 25 years; today, more than 67 percent of all BMW sold elsewhere in the world are diesels.

Current Models:
Engine: 3.0-liter I6, variable twin turbos, direct injection
Output: 265 hp @ 4200 rpm, 425 lb-ft @ 1750 rpm
0-60 mph: 6.0 sec.
Efficiency: 23/33 mpg
X6 xDrive35d
Engine: 3.0-liter I6, variable twin turbos, direct injection
Output: 265 hp @ 4200 rpm, 425 lb-ft @ 1750 rpm
0-60 mph: 6.8 sec.
Efficiency: 19/25 mpg

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