A number of experiments were carried out with fresh and aged high surface area Ce0.68Zr0.32O2 mixed oxide samples with complex feed-streams in order to determine their performance as three way catalyst (TWC). The results confirmed the oxygen storage capacity (OSC) of these samples, which favour NO conversion in cycled versus stationary stoichiometric operation. Several experiments carried out with different feed-streams have shown that a pre-reducing treatment can significantly improve both NO reduction at low-temperature and selectivity to N-2, which can be very useful to reduce the emission of nitrogen oxides immediately after starting the automobile. Although a significant reduction of the specific surface area of the mixed oxide takes place during ageing at 1173 K, it has been shown that the performance of the sample remains similar or even better than when fresh, due to an increased OSC. Thus, the reduction of CO and hydrocarbon emissions during start could be achieved by situating the catalytic converter nearer the exhaust to the engine, where the catalyst will be heated faster.