Due to increasing air pollution and decreasing fuel reserves, the search for environmentally friendly fuels continues and a lot of time and money are spent in the experiments for these searches. Therefore, it is very important to be able to determine the optimal parameter levels for a fuel's use in the engine through several experiments. For this purpose, in this study, the design of experiments (DoE)-based response surface methodology (RSM) was used to determine the optimum compression ratio (CR), engine load, and 1-heptanol percentage in a spark ignition (SI) engine to obtain the best performance such as brake thermal efficiency (BTHE), brake specific fuel consumption (BSFC) and emission values such as carbon monoxide (CO), carbon dioxide (CO2), hydrocarbon (HC) and nitrogen oxide (NOx). The data required for the RSM model were obtained from the experiments performed at three different 1-heptanol percentages (0, 10%, and 20%), three different CRs (6.0:1, 8.0:1, and 10.0:1), and three different engine loads (4, 8, and 12 kg). Optimum operating parameters to achieve the best performance and emission values were determined as 8% 1-heptanol, 10.0:1 CR, and 6 kg engine load. The BTHE, BSFC, CO, CO2, HC, and NOx, were found to be 26.03%, 0.32 kg/kWh, 0.56%, 15.07%, 182.54 ppm, and 676.16 ppm according to optimum working parameters, respectively. In addition, according to the validation study, the error rates between the optimum results and the experimental results were acceptable between 0.74% and 8.96%. Experimental results reveal that 10% 1-heptanol addition improved BTHE and BSFC by an average of 5% and 2.5%, respectively, but did not affect NOx, much. With the addition of 20% 1-heptanol, the CO emission was improved by an average of 8.5%. In terms of HC and CO2, the effect of 1-heptanol was negative. By increasing the compression ratio to 10, BTHE, BSFC, CO, and HC were positively affected, while CO2 and NOx emissions were negatively affected. It is thought that this study will be a reference study since it provides optimum operating parameters of the engine when 1-heptanol will be used as an alternative fuel in the gasoline engine. (C) 2020 The Author(s).