Officials take aim at unleaded after lowering sulfur in diesel
Now that ultra-low-sulfur diesel has been rolled out nationwide starting in 2007, U.S. regulators are now turning their attention to a far more widely-used fuel among everyday drivers, gasoline. The transition from low to ultra-low sulfur diesel fuel saw a reduction from 500 parts per million (PPM) to just 15 PPM, and is credited with enabling the introduction of more advanced injection and emissions technologies for newer-model diesel engines. Sulfur is believed to be a major contributor to diesel particulate emissions, and the move to ULSD has largely changed the perception of diesel engines as being gross polluters. Ironically, gasoline currently sold in the U.S. has a higher sulfur allowance than diesel fuel, at 30 PPM. The goal is to reduce the sulfur level in gasoline to 10 PPM starting in 2017, with an eight-year phase-in ending in 2025.