An Overview of Unocal's Low Emission Gasoline Research Program

Results from two separate emission test programs using a fifteen fuel test matrix in which ten key fuel properties were independently varied have shown that changes in gasoline distillation characteristics, olefin content and Reid vapor pressure (RVP) can produce major changes in total tailpipe exhaust emissions. All other variables examined, including oxygen content and aromatic content of the fuels, did not directly affect the tailpipe output of carbon monoxide, nitrogen oxides, or hydrocarbon emissions. From these results a generalized mathematical model was produced which predicts tailpipe emission changes from key fuel properties. The model was verified in a separate, 13 vehicle study.