Developing and designing fuel efficient vehicle for a one gallon of fuel marathon is a challenging task. Engines have to be optimized to achieve maximum fuel efficiency. In this study, we evaluate the optimal compression ratio (CR) and ignition timing that produce the best torque in a custom gasoline-based-motorcycle-engine that use ethanol E100 fuel. In the first experiment, CR was adjusted between 9 and 12 to evaluate its effect on the engine mileage’s record. The experiment was conducted on the test track. In the second experiment, Ignition timing was adjusted by a custom-made engine control unit (ECU) between 15° and 45° before top dead center (BTDC). The engine performance was investigated in terms of best torque and brake specific fuel consumption (BSFC), with variation of engine speed between 1500 and 8000. The test was conducted on dynamometer. The test was also performed in constant compression ratio and stoichiometric air-fuel ratio, 9. The best result is used to develop the clean, sustainable, and efficient small urban car for Shell Eco-marathon Asia competition. We achieved the best CR of 12 with the average mileage of 212.3 km/liter. The lowest BSFC is obtained at 4500 rpm, which generates 9.68 N.m.