During the production of PVC articles a composition was prepared with different additives that give the required exploitation properties. Among these additives there are viscosity regulators which are capable of changing PVC pastes viscosity over a broad range. There is quite a large variety of viscosity regulators, though in recent times a growing interest is generated by viscosity regulators made of renewable plant-based raw materials that feature high environmental indicators. Mostly, these are fatty acid methyl esters obtained through transesterification of vegetable oils with methanol. However, it is possible to use ethyl, propyl and butyl esters of fatty acids as viscosity regulators. In this connection it leads to a problem of chemical compounds identification. The most simple and effective method to identify such compounds is to use retention indexes based on gas-liquid chromatography. Experimental identification of retention indexes of 18 methyl, ethyl, propyl and butyl esters of fatty acids С16-С22 within a temperature range of 240-280°C was carried out. It shows the linear dependence of retention indexes on temperature for all esters. Equations to predict retention indexes of fatty acids esters were found.