Phase 1: Effect of Fuel Octane on the Performance of Two Euro 4 Gasoline Passenger Cars

Report no. 13/16: This report details work that was carried out to study the response of modern gasoline passenger cars on octane. The objective of this phase 1 of the study was to investigate the effect of RON and MON on the power and acceleration performance of two Euro 4 gasoline vehicles under full throttle acceleration conditions. Fifteen fuels covering RON levels 95 to 103 and sensitivities (RON minus MON) up to 15 were blended and tested. Both pure hydrocarbon and blends containing ethanol or ETBE were included so that any specific effects of oxygenates could be identified.

Three additional fuels, covering RON as low as 86, were blended using primary reference fuels. The results confirm the findings of previous studies on older vehicles by other workers that MON is not a good predictor of vehicle acceleration performance in more modern vehicles and in fact high MON levels increase acceleration time under full throttle conditions. In addition, it was found that during wide open throttle conditions efficiency deteriorated on the lowest octane (RON) fuels tested as expected as the engine adapts to knock. It was also observed that efficiency increased up to higher octane levels than would be expected for both vehicles.