Effect of Diesel Fuel Properties on Fuel Economy and Emissions of Three Passenger Cars

Report no. 2/19: The objective of this project was to assess the effects of varying diesel fuel properties associated with increasing FAME content on pollutant emissions and fuel consumption of light-duty vehicles. To that aim three passenger cars were tested, each one of them equipped with a different exhaust after-treatment system and complying with different European emissions standards, - Euro 4, 5 and 6. Four diesel fuel properties were examined namely density, cetane number, biodiesel (FAME) content and Polycyclic Aromatic Hydrocarbon (PAH) content. The study focused on the effect of potentially increasing FAME content in the fuel above the current 7% limit to help meet the original renewable energy directive (RED) obligations.

Tests included two driving cycles, the New European Driving Cycle (NEDC) and the Worldwide Harmonized Light Duty Test Cycle (WLTC), as well as a steady-state point for the characterization of particle emissions. Changes were then statistically modelled to look for trends in the data. Some established trends were confirmed but overall the effect of increasingly sophisticated after-treatment system, vehicle calibration and test cycle clearly dominated over fuel effects for emissions and efficiency in this study where changes in fuel properties were relatively small.