A universal computer model simulating the performance and fuel consumption of vehicles operating under both steady and dynamic driving conditions was developed and verified. The model calculations were based on the total vehicle's aerodynamic drag, grade and rolling resistance, atmospheric conditions and other vehicle design parameters. These include engine capacity, fuel injection and ignition method, fuel specification, drivetrain details (manual/automatic transmission), total vehicle weight and type of engine management system. The dynamic driving conditions were simulated by the European driving cycle (80/1268/EWG) which accounts for town and open roads driving conditions. The developed model was of a modular structure and was designed to run on a Pentium personal computer of a minimum of 16 Megabytes of RAM capacity. Verification of the model was achieved by comparing the predicted fuel consumption and other performance parameters, under steady and dynamic driving conditions, with the manufacturer data of a common passenger's car. An excellent quantitative agreement was obtained. The overall results demonstrated the versatility and benefits of using the developed model in the early stages of the vehicle's design process.