Ultra-low-sulfur diesel (ULSD) is diesel fuel with substantially lowered sulfur content. Since 2006, almost all of the petroleum-based diesel fuel available in Europe and North America has been of a ULSD type.
Ultra-low-sulfur diesel fuel was proposed by EPA as a new standard for the sulfur content in on-road diesel fuel sold in the United States since October 15, 2006, except for rural Alaska which transferred in 2010. California has required it since September 1, 2006. This new regulation applies to all diesel fuel, diesel fuel additives and distillate fuels blended with diesel for on-road use, such as kerosene, however, it does not yet apply to railroad locomotives, marine, or off-road uses.
Before EPA began regulating sulfur in diesel, diesel fuel contained as much as 5,000 parts per million (ppm) of sulfur. EPA began regulating diesel fuel sulfur levels in 1993. Beginning in 2006, EPA began to phase-in more stringent regulations to lower the amount of sulfur in diesel fuel to 15 ppm. This fuel is known as ultra-low sulfur diesel (ULSD).
EPA’s diesel standards target emissions from two different sources:
Onroad (or highway) vehicles; and
Nonroad engines and equipment.
Collectively, diesel standards reduce harmful emissions from both onroad and nonroad diesel sources by more than 90%.
Onroad (Highway) Diesel Fuel Standards
From 2006 to 2010, ULSD was phased in for onroad diesel.
After 2010, EPA’s diesel standards required that:
All highway diesel fuel supplied to the market be ULSD; and
All highway diesel vehicles must use ULSD.
Regulations for emissions from commercial trucks and buses