## 4 Conclusions  
The experimental WLTC tests conducted on the Toyota Prius II hybrid vehicle provided a comprehensive understanding of the changes in energy and environmental performance when gasoline (E0) is substituted for gasoline-bioethanol blends E10 and E70. The study uses synchronised data from the vehicle load bench, fuel mass gauge, diagnostic equipment, and exhaust gas analysers to numerically analyse vehicle specific parameters. 1. The fuel E0 was replaced by E10 and E70, resulting in an increase in fuel mass consumption of -0.1% and -23.9%, respectively, due to the decrease in the lower calorific value of the fuel. The higher ethanol density of E70 resulted in a smaller increase in volumetric fuel consumption (-19.1%) compared to mass consumption. The ICE of the hybrid car using E0 is quite efficient, with a \(BTE\_WLTC\approx 0.346\) compared to a conventional spark ignition engine operating at low loads, as the hybrid system  
Figure 9: CO\({}_{2}\) concentration and emission during the WLTC, using different fuels: (**a**) Before the catalytic converter; (**b**) After the catalytic converter. ensures engine operation in efficient modes. Increasing the bioethanol concentration to 10% and 70% resulted in an additional significant efficiency increase (~2.8% and ~9.0%), attributed to the more efficient combustion of bioethanol and the advanced ignition timing enabled by the higher knock resistance. 2. Upstream of the catalytic converter, CO emissions with fuel E0 were reduced by 19% when E0 was substituted with E10 and E70. The use of the catalytic converter reduced CO emissions with E0 by approximately 170 times. Similarly, the substitution of E0 with E10 and E70 reduced unburned hydrocarbons by approximately 17% and 27%, while downstream of the catalytic converter, HC emissions with E0 were reduced by approximately 80 times. The addition of 70% bioethanol further reduced CO and HC emissions downstream of the catalytic converter by ~28% and ~15%, respectively. The reduction in CO and HC emissions can primarily be attributed to the increased oxygen content in the fuel mixture due to bioethanol, the lower C/H ratio, and the advanced ignition timing. However, it was observed that in low- and medium-speed driving modes, the higher frequency and duration of braking caused a reduction in exhaust and catalytic converter temperatures. This effect was further amplified with an increasing bioethanol concentration, due to the higher specific evaporation temperature and earlier ignition timing. As a result, CO and HC emissions were higher in these driving modes, and pre-catalytic converter and catalytic converter efficiencies were lower. 3. Direct NOx emissions from the ICE were reduced by approximately 24% and 30% when E0 was replaced by E10 and E70, respectively. The catalytic converter reduced the NOx emissions of E0 by approximately 74 times. The addition of bioethanol further reduced NOx emissions by approximately 16% and 21%. However, in the low- and medium-speed vehicle modes, increasing the bioethanol concentration in the fuel led to an increase in NOx emissions. This was because the advanced ignition timing at lower engine speeds resulted in a greater rise in combustion temperatures, promoting NOx formation, while the lower exhaust gas temperatures reduced the catalytic converter's efficiency. The most significant positive effect of bioethanol was observed in the high- and very-high-speed vehicle modes, where the hybrid system's electric motor assistance is relatively lower and the ICE bears a higher load. In these conditions, the higher bioethanol content enhanced cylinder cooling, reducing high-temperature NOx emissions, while the catalytic converter temperatures were similar to those with E0 and effectively reduced NOx emissions. 4. The specific CO2 greenhouse gas emissions upstream of the catalytic converter when running on E0 fuel were 138.8 g/km. The oxidation of CO and HC compounds in the catalytic converter resulted in an increase of approximately 5.9% in CO2 emissions to 153.8 g/km.