Bio diesel is as clean as any yet the U.S. put a restriction on VW and Benz, the current world leaders in clean diesel technology and resricted (stopped) their sales here. Funny how the time frame correlated with the push for flex fuel and yet the Hummer owners keep rolling along with a tax credit if they apply for status as a farm vehicle due to their weight. Oh what a world, what a world, I'm melting.