With the widespread introduction of the third generation additives to modern gasolines, Phillips Petroleum Company chose to further define the effects of gasoline/ethanol blends (gasohol) on intake system deposits (ISD). The third generation additives referred to here are those that provide protection against ISD. This paper presents detailed results of the investigation in this area.During evaluation of various ISD additives, it was found that additive levels capable of controlling ISD with normal gasolines were unable to do so with fuels containing neat ethanol. Most fuel grade ethanol available in the marketplace is pretreated with additives intended to control accumulation of port fuel injector (PFI) deposits. These currently accepted PFI additives proved to be even more of a problem to intake valves than neat ethanol in gasoline. Some, however, contributed more to valve deposits than others.Data for this investigation was generated via the Modified IVD Test in BMW vehicles at an independent laboratory. Results identify that proper gasoline and ethanol additive combinations and treatment levels can provide satisfactory ISD protection in gasoline engines.