The influence on the ion current from a variety of fuels and additives has been investigated. The ion current has been measured in an engine as well as in a continuous atmospheric burner. The acquired ion current data has been statistically treated in order to find general trends and behaviors. The measurements were found to be in agreement with established theories for the ion current formation. This work indicates that the use of alternative fuels will not endanger the large engine control potential supplied by the ion current technique, since the changes induced by the fuel variety can be accounted for, when using the different fuel types of today.