Impact of diesel and detergent contamination on gasoline low-speed pre-ignition and their characterization using unwashed gums

•Gasoline contaminants contribute to enhance pre-ignition.•Contaminant effect on pre-ignition is directly related to gasoline formulation.•Detergent additive can have both a positive and a negative effect on pre-ignition.•The correlation emissions and pre-ignition is valid for the selected contaminants.•Unwashed gums can detect and quantify diesel and detergent within gasoline fuel.•The results suggest a correlation between unwashed gums and low speed pre-ignition frequency. Fuel composition variability affects many aspects of engine operation. This includes the propensity to trigger abnormal combustions. Fuel logistic can lead to incorporating different contaminants into gasoline. Diesel fuel or over-concentrated detergent additives are two examples. They require a qualification and quantification within the gasoline fuel and an evaluation of their impact on engine performances. We consider both contaminants in this work and it addresses simultaneously their identification within a gasoline fuel and their impact on abnormal combustion. The study evaluates contaminants propensity to trigger Low Speed Pre-Ignition (LSPI). The latter is a stochastic abnormal combustion leading to engine damage related to fuel quality. A novel method based on unwashed gums is used to characterize qualitatively and quantitatively these contaminants. Engine tests led to the conclusion that diesel contamination contributes to increase LSPI frequency and severity. However, this increase depends on the base fuel heavy aromatic content. Deposit control additive (DCA) increases slightly LSPI frequency compared to diesel contaminant. The study also suggests that such additive can contribute to recover a less sensitive combustion system once it has been running with a diesel contaminated gasoline. Finally, this work explores the possibility of correlating fuel propensity to trigger LSPI through unwashed gums (UWG) measurement. It concludes that the approach seems sensible but requires further work to be confirmed.