Utra-Low
Sulfur Diesel Fuel (ULSD)
A
diesel fuel a sulfur content of 15 parts per million (ppm)
or lower. Ultra-low sulfur content in diesel fuel is beneficial
because it enables use of advanced emission control technologies
on both light- and heavy-durydiesel vehicles. The combination
of ULSD with advanced emission control technologies is sometimes called "clean
diesel."
Nitrogen oxides and particulate matter are the two most harmful
diesel pollutant emissions. These can be controlled with the
use of catalytic converters (for nitrogen oxides)
and particulate traps. However, sulfur -- in amounts that
used to be allowable in diesel fuel -- deactivates these devices
and nullifies their emissions control benefits. Using ULSD
enables these devices to work properly.
In general, ULSD should cause no noticeable impact on vehicle
performace, although fuel economy might be slightly reduced
because the process that produces ULSD can also reduce the
fuel's energy content. Removing sulfur from diesel reduces lubricity; however, this problem can
be solved by introducing special additives. Blending biodiesel with ULSD also increases lubricity.
Using ULSD in older diesel vehicles might affect fuel system
components or loosen deposits in fuel tanks. These vehicles
should be monitored closely for fuel system problems and premature
fuel filter plugging during the transition to ULSD. New vehicles
designed to use ULSD must never be fueled with a higher-sulfur
fuel. If kerosene is blended with ULSD for improved cold-weather
performance, it must be ultra-low sulfur (15 ppm or lower)
kerosene. New engine oils have been developed for use with
new diesel vehicles fueled with ULSD.
Currently, the vast majority of ULSD is made from petroleum.
However biodiesel, biomass-to-liquids and gas-to-liquids diesel,
and hydrogenation-derived renewable diesel are inherently
ultra-low sulfur fuels and could help meet ULSD requirements
in the future.
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