The effects of fuel volatility and alcohol content on vehicular performance were determined in unmodified conventional, prechamber stratified charge, and direct injection open-chamber stratified charge vehicles. A clear water-gasoline emulsion fuel was included in the test sequence. Driveability testing revealed that the stratified charge powered vehicles were relatively insensitive to base fuel volatility. Driveability depreciated with increasing alcohol content for all vehicles. Testing of the water-gasoline emulsion showed driveability was unsatisfactory in vehicles powered with conventional and prechamber stratified charge engines but marginally acceptable in the open-chamber stratified charge engine. Increasing alcohol content up to 20 V % increased mass emissions of the open-chamber stratified charge engine, reduced emissions of the prechamber stratified charge engine, and had no significant effect on the conventional engine. Fuel economy on an energy utilization basis was improved with increasing alcohol content and reduced with the water-gasoline emulsion.