The article presents a method based on the theory of cumulative fuel consumption. The outline of the method is presented using data from long-term (many years), natural operation of a middle-class passenger car covering a mileage of over 320,000 km and 647 refuelings. The results of the research and analyses turned out to be extremely adequate to the operational data. The correlation coefficient of the mathematical model describing CFC (cumulative fuel consumption) as a function of mileage (km) was R2>0.9999. Such an analysis result can be the basis for determining the ICFC (intensity of cumulative fuel consumption) and SCFC (specifically cumulative fuel consumption) courses as a function of mileage curves (irrespective of other parameters, such as ambient temperature). The three models mentioned together constitute the energy footprint of the vehicle. It has been shown that the assessment of vehicle fuel consumption created solely on the basis of known indicators, such as FE (average fuel consumption between cycles or its average value (AFE) may not be adequate for assessing the fuel consumption of the car engine- and that is the and this is a new finding in the literature on this topic.