The study analyses the effect of acceleration intensity on energy consumption and drive efficiency during a road test for a passenger vehicle. The acceleration was carried out from the assumed initial speed to the target speed determined appropriately for individual gear ratios. The tested speeds include values of 40-130 km/h. The intensity of the acceleration process resulted from the selected settings in the powertrain, such as the throttle opening with values from 30 to 100% and gearbox ratio selection. The tested mean accelerations covered the values from 0.2 to 1.5 m/s2. For individual sets of acceleration intensity, gearbox ratio and throttle opening, the unit energy consumption curves and the total efficiency courses of the powertrain system were determined. The average values of the powertrain efficiency obtained during the acceleration tests amounted to the range of 19.38–25.67%, while an increase in the average efficiency was found with a decrease in the gear ratio value and also the influence of the throttle opening was observed. The study assessed also the relationship between the average acceleration for the speed gaining phase and unit energy consumption, where the acceleration increment by 0.1 m/s2 causes a proportional increment in unit total energy consumption by about 0.15J·(kg·m)−1, regardless of the acceleration intensity.