Kualitas bahan bakar yang baik akan memperbaiki performa kerja mesin dan menurunkan emisi gas buang kendaraan bermotor. Salah satu cara untuk meningkatkan kualitas bahan bakar adalah dengan mencampur bahan bakar dengan aditif. Penggunaan bahan organik beroksigen [oksigenat] sebagai bahan pengungkit angka oktana bahan bakar semakin mendapat perhatian diIndonesia karena senyawa timbal yang selama ini banyak dipakai dapat menimbulkan pencemaran udara. Campuran oksigenat dalam bahan bakar dapat memperbaiki kulitas pembakaran, memperbaiki unjuk kerja mesin serta menurunkan emisi gas buang. Penelitian ini akan membahas tentang pengaruh campuran bahan bakar dan aditif pada engine 4 langkah berbahan bakar pertamax. Ppenelitian akan dilakukan diLaboratorium Thermodinamika Teknik Mesin UI. Performa kerja yang akan dianalisa adalah daya efektif poros, efisiensi thermal dan konsumsi bahan bakar spesifik, sedangkan gas buang yang ditinjau adalah HC, CO, CO2, O2, dan NOx. Kompresi rasio diambil dari kondisi standar motor sebesar 8,2:1. Penambahan aditif pada pertamax menurunkan emisi HC, CO, dan O2, sedangkan emisi CO2 dan emisi NOx naik. Daya dan efisiensi thermal secara umum naik sekitar 11,11% dan terjadi penurunan sfc sekitar 18,54%. Berdasarkan data, performa bahan bakar pertamax + campuran oksigenat hampir sama baiknya dengan performa Pertamax Plus.

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Good fuel quality will improve engine performance and reduce exhaust emission of vehicle. One of the way to increase fuel quality is by adding additive into fuel. The usage of oxygen organic compounds (oxygenate) as octane booster is nowdays concerning in Indonesia because the lead compound that already been used all this time could cause air pollution. The oxygenate compound contains in the fuel may improve burning qualities, machine performance and also decrease gas emission. Will be discussed about effect of fuel and additives mixture on four stroke engine with Pertamax as fuel. Research was held at Thermodynamic Laboratorium, Mechanical Engineering Departement UI. Engine performance analyzed were effective horse power, thermal efficiency, and brake specific fuel consumption, while exhaust emission evaluated were HC, CO, C02, O2, and NOx. Compression ratio taken from standard engine, that is 8,2:1. Additives addition on Pertamax decreased HC, CO, and O2 emission, while exhaust CO and NOx emission raised. So that horse power and thermal efficiency raise up around 11,11% in general, and brake specific fuel consumption drop about 18,54%. Based on data, performance of Pertamax + oxygen organic compounds (oxygenate) fuel as well as Pertamax Plus fuel's performance.