Most drivers are aware of ultra-low sulfur diesel (ULSD), which was introduced on a widespread scale in 2006 and was mandated as the way all diesel would be blended shortly afterwards.  ULSD is just what it’s name implies: diesel fuel with a lower sulfur content.  Nearly all diesel fuel sold in North America is now ULSD.

Most trucks now are built to use ULSD, especially models built after 2006.  Engines before that time will likely require a lubricity enhancement additive unless using biodiesel or other more viscous fuels.  This is because the sulfur in the diesel fuel before ULSD acted as a lubricant in much the same way graphite is a lubricant for some applications.

ULSD was introduced as a way to lower some emissions and the Environmental Protection Agency then mandated its use nationally in the U.S.

ULSD lowers nitrogen oxides (NO_x) and particulate matter from diesel fuel emissions.  NO_x are the primary ingredients in several chemical-air mixtures that result in smog, including low-level ozone.  Particulate matters are the black smoke often attributed to diesel engines, despite today’s engines filtering, re-burning, or otherwise disposing of most of these without releasing them into the atmosphere.

The wide-spread adoption of ULSD has done much to curtail the emissions of diesel-fueled vehicles, which make up about 1/3 of the motor fuel use in the United States.  The adoption of ULSD is becoming world-wide.

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