To determine the amount of air pollutants, produced by Iranian automakers, and compare it with old and retrofitted vehicles have become one of the important tools of urban management. The present research uses International Vehicle Emission (IVE) modeling software in order to verify SAIPA Co. fleet emissions, based on Euro 4 emission standard (SAIPA Co. recognized as a superior Iranian brand in vehicle industry). There has been attempts to determine pollutant emission from Saipa Co.-manufactured cars in the city of Tehran, in accordance with Tehran Driving Cycle along with modeling and lab results which have over 90% conformity with modeling and lab results of New European Driving Cycle. According to ISQI’ s 100, 000-km test results, the amount of CO2 emission modeling from X100 and Tiba2’ s has been about 160 gr/km, which has been within the range, whereas the modeled CO2 emission rate has been 232 gr/km in TDC, i. e., 1. 5 times more than laboratory test, due to different driving cycle usage. Significant differences between the values obtained in the emission lab and modeling at New European Driving Cycle, Tehran Driving Cycle, and Tehran Air Quality Control Company report, indicate that relying on hypothetical situation leads to inapplicable emissions value from light vehicles.