A Comprehensive Examination of the Effect of Ethanol-Blended Gasoline on Intake Valve Deposits in Spark-Ignited Engines

Ethanol-gasoline blends are widely understood to present certain technical challenges to engine operation. Despite widespread use of fuels ranging from E5 (5% ethanol in gasoline) in some European countries to E10 (10% ethanol) in the United States to E100 (100% ethanol; “alcool”) in Brazil, there are certain subjects which have only anecdotally been examined. This paper examines two such issues: the effect of ethanol on intake valve deposits (IVD) and the impact of fuel additive on filter plugging (a measure of solubility). The effect of ethanol on IVD is studied along two lines of investigation: the effect of E10 in a multi-fuel data set carried out in the BMW 318i used for EPA and CARB certification, and the effect of varying ethanol content from 0% to 85% in gasoline carried out in a modern flex-fuel vehicle. While different detergent types are shown to effectively reduce IVD in a range of ethanol concentrations, the potential effects of fuel additive solubility on fuel filter plugging are shown to vary with dose and type of detergent additive, including variations within a single additive type.