I've been saying this for years and I do not consider myself to be very smart. They've had them for decades in Europe and the reason the US will not get them is they stink, smoke, sound like trucks, and cost a lot exactly like your paternal grandfather did before he died. The latest turbodiesel engines from Mercedes, BMW, and Volkswagen are free from all of these problems. The only problem now is how to get to economies of scale going on an expensive engine that burns a completely new fuel. The price per unit has to come down, and it will not come down without the help of tax cuts for companies making the engines and consumers buying the cars. Hybrid turbodiesels burning jatropha and switchgrass biofuel will hold the US over for decades until better batteries come around and hydrogen cell technology finally matures.