The diesel vehicle segment got a big shakeup around 2007, as the nationwide phase-in of ultra-low-sulfur diesel (ULSD) fuel began. Although unpopular with oil companies for the added processing involved, the usage has proven a net positive for the industry and consumers, as it has facilitated the importation and development of many more diesel engines from Europe and elsewhere, which have run on lower-sulfur diesel for many years. Now that diesel emissions are largely in check thanks to the higher-quality fuel and emissions aftertreatment, U.S. regulators are taking a closer look at the sulfur content of unleaded fuel, Bloomberg reports.

While already much lower than that of diesel before ULSD, which had a proportionally high 500 parts per million (PPM), current unleaded gasoline still has a higher sulfur level at 30 PPM, compared with ULSD, which has a maximum allowable concentration of 15 PPM.

The ultimate goal for sulfur content in gasoline is 10 PPM, with an eight-year phase in from 2017 to 2025. The measure is reportedly supported by automakers that already build cars for markets with stricter fuel-quality requirements, and would save engineering and development costs calibrating for a single fuel standard rather than specific calibrations for each market.

Oil companies have voiced opposition to the measure, claiming it will increase their capital and compliance costs by billions of dollars. The EPA claims the new standards could prevent as many as 2400 premature deaths a year through cleaner air and result in a savings of up to $23 billion in related health care costs.

The final factor bringing scrutiny to gasoline fuel quality is the increased prevalence of gasoline direct-injected (GDI) engines. While GDI engines have an efficiency advantage over port fuel injection, they do have a tendency to have higher particulate emissions, an issue that is exacerbated by higher concentrations of sulfur.

Source: Bloomberg