California Air Resources Board

The California Diesel Fuel Regulations, Sulfur Content of Diesel Fuel, and Aromatic Hydrocarbon Content of Diesel Fuel, were adopted by the California Air Resources Board (CARB) at the end of 1988 and were implemented in 1993.  The original sulfur standard of 500 ppmw was lowered to 15 ppmw in a 2003 rulemaking that was implemented in 2006.  Most California diesel fuel is produced to the specifications of proprietary formulations, which have been certified to be emission-equivalent to the aromatic hydrocarbon standard of 10 percent by volume.  The 2003 rulemaking also provided an additional compliance option, the Designated Equivalent Limits, for meeting the aromatic hydrocarbon standard, beginning in 2004.  The Designated Equivalent Limits are specifications of an emission-equivalent formulation that may be used by any California diesel fuel producer or importer.

The California Diesel Fuel Regulations apply to essentially all diesel fuel supplied, sold, or offered for sale in California.  The original applicability of the regulations was to vehicular diesel fuel; however, the applicability of the regulations has been extended by the adoption of Airborne Toxicant Control Measures (ATCMs) to non-vehicular diesel fuel, such as fuel for stationary engines, locomotives, and marine harbor craft.