The increasing volume of motorized vehicles leads to an increase in dependence on fossil fuels and an increase in air pollution. The problem can be reduced by utilizing renewable alcohol fuels such as methanol, ethanol, and butanol. The high number of octane and oxygen content is the main reason. Therefore, this study aims to observe the exhaust emissions of the 160 cc gasoline engine with a mixture of methanol, ethanol, and butanol. The percentage of alcohol used is 0 % to 30 % by volume. The test was carried out in 2000, 3000, and 4000 rpm. The results of the study explained that the use of methanol, ethanol, butanol in the fuel mixture was proven to reduce exhaust emissions. CO and HC emissions decreased as the percentage of alcohol in the fuel increased. The highest reduction in CO and HC emission in methanol blended fuel was 30 %, 94.55 % and 82.71 %, respectively. Meanwhile, CO2 emissions increased by 34.88 % at 2000 rpm engine speed. Based on this test, the addition of methanol to fuel can reduce exhaust emissions better than ethanol and butanol.

The growth of diesel vehicles has consequences for the consumption of diesel oil. Therefore, using Jatropha as an alternative fuel reduces dependence on diesel oil and it does not interfere with food availability. However, the high viscosity of jatropha oil makes the fuel pump work harder. In addition, the low calorific value reduces the quality of the fuel which creates unique problems. Ethanol, with its low viscosity and high oxygen content, is expected to be effective in reducing jatropha problems for diesel engines. Therefore, this study aims to evaluate the addition of ethanol to the brake torque, brake-specific fuel consumption, exhaust gas temperature, and smoke opacity. The 4JB1 diesel engine with an EGR was tested on a 10% (DJ10) and 20% (DJ20) diesel-jatropha mixture. The experimental results showed that brake torque increased by 1.51% in the DJ10 application, brake specific fuel consumption decreased by 7.05%, exhaust gas temperature decreased by 0.67%, and smoke opacity increased by 25.91%. While in the DJ20 application, brake torque increased by 3.19%, brake-specific fuel consumption decreased by 30.08%, exhaust gas temperature decreased by 0.67%, and smoke opacity increased by 69.03%.

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Human dependence on motorized vehicles is getting higher and uncontrollable. This actualization will certainly have an impact on reducing fuel stocks and air pollution with soot emissions. Combining diesel fuel with jatropha and alcohol is predicted to reduce dependence on diesel fuel and air pollution. Supplying the combustion chamber with exhaust gas/Exhaust Gas Recirculation/EGR is also predicted to reduce soot emissions and reduce fuel consumption. This study aims to observe the effect of using the EGR system on the use of mixed fuel jatropha and ethanol exhaust gas temperature/EGT as an indication of performance and soot/smoke opacity as exhaust emissions. The experimental results show the use of the EGR system increases EGT and Smoke opacity decreases the diesel engine in each fuel variation. D100 fuel EGT increased 1.67%, DJ10 increased 0.71%, DJ10E increased 0.67%, DJ20 increased 1.45%, DJ20DE increased 1.07%, DJ30 increased 1.50%, and DJ30E fuel EGT increased by 1.47%. While on the emission side, the smoke opacity of D100 fuel decreased by 1.84%, DJ10 decreased by 1.71%, DJ10E decreased by 2.21%, DJ20 decreased by 0.96%, and DJ20E decreased by 2.33, DJ30 decreased by 2.99%, and DJ30E fuel decreased 1.30%.

Ethanol has higher octane and oxygen properties than fossil-fuel gasoline. Along with the increase in gasoline dependency and exhaust emissions, the use of ethanol as a fuel is urgently studied. This study aimed to observe the concentration of 5% ethanol in gasoline on the performance and exhaust emissions of a 150cc gasoline engine that was operated at 1000, 2000, and 3000rpm. The observation results show that the concentration of 5% ethanol in gasoline correlates with an increase in performance with indications of an increase in EGT, Brake power, BTE, and a decrease in SFC. On the emission side, it is also correlated with an increase in the quality of exhaust emissions with indications of increased CO2 emissions and reduced CO and HC emissions. The best correlation of 5% ethanol concentration was obtained at an operating speed of 2000rpm with an increase in EGT of 10.70%, an increase in Brake power of 9.49%, an increase in BTE of 38.62%, an increase in CO2 emissions of 23.06%, a decrease in SFC of 26 .49%, CO emission reduction of 16.67%, and HC emission reduction of 4.24%.