Transesterification does not allow to make full conversion of oil to biodiesel because the glycerol as a by-product cannot be included in the composition of biofuel. The development of methods for full conversion of raw material to biofuel with higher yield remains entirely relevant. Interesterification, a reaction of vegetable oil with methyl acetate, constitutes a full conversion process which has not been investigated sufficiently. Instead of glycerol, the interesterification reaction gives triacetin (TA) which can be included in the composition of biofuel and allows to increase its yield. Both interesterification and transesterification occur at low temperature only in presence of catalysts. Results of the investigation of heterogeneous and homogeneous catalysts indicate the superior importance of catalyst solubility in starting reaction mixture of oil and TA. Partial solubility can remarkably lower the activity of homogeneous catalyst and extremely increase that of formally heterogeneous one. The reaction mixture of interesterification reaction is less polar than that of transesterification, and potassium tert-butoxide (t-BuOK) should be more appropriate catalyst for interesterification than sodium methoxide which is used in most cases. The catalytic system t-BuOK/t-BuOH substantially increases the yield of TA and changes the properties of obtained biofuel. Whereas the content of the TA in the interesterification reaction mixture does not achieve the same level from the theoretically predicted as the FAME, the occurrence of side reaction between t-BuOH and TA cannot be excluded. This paper presents a study of the interesterification of rapeseed oil in presence of catalytic system t-BuOK/THF (catalytic system without alcohols) with the aim of establishing the influence of aprotic tetrahydrofuran to the proceeding the reaction, composition of reaction mixtures and their fuel properties. Obtained results show that the absence of alcoholic hydroxyl groups in the catalytic system insufficiently increases the activity of catalytic system but fails to increase the yield of TA. The content of TA increases and fuel properties become more conformable with the requirements for biodiesel standard only by an increase of methyl acetate to oil molar ratio from 18 to 27.