Lubricity of California Diesel Fuel

Diesel fuel marketed in California has been subject to aromatic content and sulfur content standards since October 1993. Low sulfur diesel has been marketed in Southern California since 1988. To insure quality of the reformulated fuel, California Air Resources Board staff monitored the lubricity of California diesel from October 1993 through the end of 1996, using data from the Scuffing Load Ball-on-Cylinder Lubricity Evaluator (SLB-OCLE). Sulfur and aromatic content of sampled fuels were also determined. Over the three year period of the study, the production-weighted lubricity of California diesel was consistently at or near 3000 grams on the SLB-OCLE. The SLBOCLE results have improved over the course of this study, likely due to a shift in the formulation of diesel products marketed in California. Refiners have used lubricity additives in low sulfur, low aromatic content (10% volume) diesel. Rather than reducing aromatic content to 10%, many California refiners are now relying on the use of alternative formulations to obtain the required emission reductions. Finally, no lubricity-related fuel pump damage has been documented for California vehicles.