The efficiency of an internal combustion engine can be calculated using the power that reach the wheels and the chemical power released by the fuel. This happend because only a part of the chemical power can actually reach the wheels in order to move the vehicle, this part is defined by its global efficiency. The global efficiency is composed of other efficiencies of each elemento where the power is transmitted until it reaches the wheels, like the engine efficiency and the transmission efficiency. The present work has the objective of calculate the fuel consumption using the chemical power in every moment. With this, intrinsic parameters of the vehicle will be changed, like its mass, drag coeficiente and rolling coeficiente, and will be calculated the fuel consumption for each case. Using the results found an analysis will be made on how each parameter influenced the vehicles global efficiency. For the calculation will be developed a model that will simulate in a quick way the consumption for each case. This simulation is based on the theory of the vehicle dynamics and will use results of tests made on LEV (Vehicular Engineering Laboratory) in PUC-Rio to calibrate de model. In order to made the changes it will be necessary only to change a value in the program and immediately the new consumption will be displayed, something extremely positive that allows to get results faster than if to make a new test. The main feature being examined is the vehicles mass and its influence on the efficiency compared to the other features. To do the simulation it only needs some vehicle information and the cycle that will be applied.