Biodiesel fuel is a fatty acid alkyl ester, commonly synthesized via transesterification of triglycerides (vegetable oils and animal fats) with an alcohol, in a presence of a catalyst. Production of biodiesel fuel from waste vegetable oil eliminates additional costs of growing oilseed plants as a raw material, reduces the amount of waste in the food sector, preserves fertile land area and water, eliminates direct competition with food which could otherwise potentially lead to price increase and shortages of edible vegetable oils. The structure of the biodiesel molecule depends on the feedstock from which it's synthesized. The triglyceride’s fatty acids have mainly straight hydrocarbon chains, so the alcohol molecule determines if the ester will be straight-chained or branched. The molecule structure is determinant for some diesel fuel properties. For example, longer straight-chained molecules will have higher cetane number values, while branched ones will have lower pour point values and, therefore, engines will be able to perform at lower temperatures. Cetane number is the prime indicator of the fuel quality used in the internal combustion compression engines. Some biodiesel fuels show high cetane number values. It has been proven that longer hydrocarbon chains in the ester molecules are proportionately related to the cetane number value, therefore, synthesis with higher alcohols are being tested, such as 1-Hexanol. In this research, the influence of reaction parameters on the transesterification process of waste vegetable oil with 1-Hexanol was examined. The influence of the alcohol/oil molar ratio, the influence of the mass fraction of the alkaline catalyst KOH, the influence of the reaction time and temperature were monitored. The conversion was calculated from 1H NMR spectra by integrating the surface areas of specific signals. The experimental part of the research established that 60 °C is the best temperature out of given three in the reaction. 12:1 alcohol to oil molar ratio had a higher conversion because greater excess of an alcohol shifted this reversible chemical reaction more towards the products. The catalyst mass fraction of w(KOH) = 3 % gave higher reaction yields than the 1 % one. High conversions of the reaction were obtained after only 2 minutes, but by the 15th minute the conversion increased by approximately 1.59 % and reached its near maximum. It was experimentally shown that the parameters that have the greatest effect on conversion are the mass fraction of the catalyst and the alcohol to oil molar ratio.