June 1st marked the first important step towards the ultimate phase-in of Ultra-Low Sulfur Diesel (ULSD) fuel in the U.S. by 2010. As of the first of this month refiners began producing cleaner-burning ULSD fuel for use in highway vehicles such as big rigs and buses. All 2007 and later models of these highway vehicles will be required to use the new fuel by law. Using currently available Low Sulfur Diesel fuel will not only harm these new engines, but is also illegal and may result in civil penalties.
Interestingly enough, these new engines when being fueled by ULSD will likely return worse fuel mileage than current models. Significantly reducing the sulfur content of the fuel also serves to lower the energy content, as well. That means more fuel is needed to produce the same amount of power as before, although using ULSD will mean a 90-percent reduction in polution caused by heavy highway vehicles.