So you want to go biodiesel [0], eh? Maybe you noticed that oil popped over $74 a barrel this afternoon - not quite the $95 peak of 1979, [1] but getting there. Maybe you read the energy doomsday scenarios [2] former CIA director (and hemp [3] fan) James Woolsey [4] has been pushing [5] in the media lately. Or maybe you just want the subversive thrill of using McDonald's waste [6] to power your personal green revolution.

OK, so perhaps you're not quite as high on canola oil as I am. I've got the biodiesel bug bad, and I've been jonesing for a Volkswagen and its highly regarded [7] TDI diesel engine.

Yet when I went to VW.com [8] I found, well, very few TDIs. "You know those things are impossible to find, right?" a dealer in Colorado asked me when I went looking for a TDI Jetta wagon, before advising me to check out one of their remaining TDI sedans. (Alas, my big dogs and surfeit of outdoor gear require the cargo space of a wagon.)

Word on the TDI forums [9] is that VW is offering no TDI models for 2007 and likely 2008 - no Jetta wagon, no Passat sedan, no sporty little Golf.

What gives? With the fuel efficiency and biodiesel points so urgently tipping, why is VW pulling back its diesel engine?

EPA emissions standards - much too byzantine [10] to elaborate here - are going into effect that the Volkswagen's diesels may or may not meet, putting the company's diesel offerings in a holding pattern. One piece of news that has trickled out is the company's move from the TDI-based engine to a new type of diesel fuel injection called common rail, [11] which injects fuel at higher pressures and allow for more complete combustion - and, therefore, reduced emissions. It's unclear, at least to me, whether these engines meet the tougher EPA standards. (Not really surprisingly, VW's frog-like SUV, the Touareg, [12] will be available in a massive V-10 TDI, according to a Volkswagen rep I spoke with.)

2005 was the last model year for TDI Jetta wagons, TDI Passat wagons and sedans; 2006 TDI Jetta sedans, Beetle sedans and Golfs are still available. The Jetta and Beetle sedans will be available into 2007, though as products of an extended 2006 run rather than as new models.

With the future of VW diesel in limbo (at least in the US), I'll keep looking [13] for my TDI Jetta wagon.

Photo credit: David Sterrett, [14] tdiclub.com [15]