Fuel effects on emissions from modern gasoline vehicles part 2 – aromatics, olefins and volatility effects

The influence of gasoline quality on exhaust emissions has been evaluated usingfour modern European gasoline cars with advanced engine technologies/aftertreatmentsystems. Part 1 of this report described the short-term sensitivity of thesefour cars to gasoline sulphur content. This report describes the influence of otherfuel effects: aromatics, olefins, volatility and final boiling point.Emissions from the test vehicles were all very low, in compliance with theappropriate Euro-3 or Euro-4 emission limits. The measured effects of fuel changeson the regulated emissions: NOx, HC and CO, were small and often conflicting, withdiffering directional responses for different vehicles and emissions.The three direct injection cars emitted higher levels of particulate mass (PM) thanthe advanced MPI car, although much lower than the Euro-4 diesel PM emissionlimit. Response to fuel effects was similar in the three direct injection cars. PMemissions from the advanced MPI car, which is more representative of the currentfleet, were very low on all fuels tested and insensitive to fuel changes.