Table 4 shows CO, HC and NOX emissions for the five different driving modes. It was found that for both test fuels, the higher CO emissions, even up to about 865 mg/km, were observed at intermediate cruising speeds, whereas CO emissions were lower at the idle stage and 50 km h−1. CO emissions, at idle stage and 50 km h−1, were decreased by about 14.8 and 16.9% for E10 fuel, as compared to base fuel. It is meaning to address that at intermediate cruising stages, the influence of the ethanol addition on CO emissions was insignificant as shown in Table 4.