One of the renewable fuels is ethanol, which is widely used in internal combustion engines. Ethanol is produced from renewable sources such as sugar cane, corn, potato, and biomass. It has high octane number, however, lower calorific value than that of gasoline and diesel. Since ethanol is a corrosive fuel, it cannot be used completely pure, so it is used as a mixture in internal combustion engines. Therefore, ethanol was mixed with diesel fuel to both eliminate its corrosive effect and increase its calorific value and used to examine engine performance and exhaust emissions in an SI engine at partial loads in this study. Four-stroke and four-cylinder test engine was used, and the experiments were carried out at constant speed of 2000 rpm, at 25 Nm and 50 Nm load, and with different excess air ratios (λ). The fuel mixture used in experimental studies was set as 80%Ethanol+20%Diesel (E80D20). To see the effect of the E80D20 mixture more clearly, the same experiments were also repeated with pure gasoline and pure ethanol, and these three fuel conditions were presented comparatively. At 25Nm and λ= 0.9, the use of E80D20 resulted in a 15% reduction in BSFC compared to the use of pure ethanol. When emissions are considered, the use of E80D20 in lean mixture (λ=1.1) showed a decreasing trend in HC and NOx emissions.