from the oil refinery worker: you can thank the ULSD for the increase in diesel prices in the US along with the demand for diesel over seas, we ship most of it to europe. however the new refining process cost a ton of money and are difficult, not to mention sulfur was a very lubricating component of diesel which contributed to the higher cetane rating and longer life of the engines. this is the main reason they had to build an entire new powerstroke instead of sticking dpfs on old designs, the common rail has helped tremendously and is also why the oil changes can be extended due to less oil shear. it wont be too much longer and LSD will start to be dyed like the off road diesel.