Fuel cell electric vehicles (FCEVs) are a possible sustainable and long-term solution to satisfy the demand for mobility. Cost targets are achieved by lowering platinum (Pt) loadings on the electrodes and using thinner membranes in the fuel cell system (FCS), maximizing the current density. Due to these measures, the FCS becomes more sensitive to contaminants, including those originating from crossover through the membrane. One of these contaminants - carbon dioxide (CO2) - causes effects that can be reversed, however, this process negatively influences the FCS lifetime. For this reason, operating conditions should be chosen such that minimal temporary losses are caused without causing further negative effects, such as degradation, in the FCS. This paper shows the effects of CO2 and O-2 permeation occurring during operation of an FCS and proposes the possibility of mitigating the crossover via the right choice of membrane. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.