In this paper, selected physicochemical properties such as kinematic viscosity (nu), density (rho), lower heating value (LHV), cold filter plugging point (CFPP), miscibility, flash point (FP), coefficient of friction (mu), lubricity (WS1.4), surface tension (sigma), and copper strip corrosion (CSC) diethyl ether/rapeseed oil blends were experimentally determined. Diethyl ether (DEE) was blended with rapeseed oil (RO) in volumetric ratios of 10, 20, 30, and 40%. The values of the LHV, kinematic viscosity, surface tension, and density of the blends were lower than the values obtained for the tested rapeseed oil. Especially, it was found that DEE has significant influence on the rapeseed oil viscosity value. The addition of merely 10% DEE to rapeseed oil decreased its viscosity by 50%. It was shown that the lubricity of all tested blends is reduced, but not as significantly as viscosity. Also, we confirmed that tested blends do not promos=the corrosion processes. What is more, it was found that the temperature of the CFPP decreased when DEE was added to RO and the miscibility of all tested fuel blends is excellent in a wide range of temperature changes. For this reason the results of our research suggest that DEE/RO blends seem to be usable for engines operated in the winter season. However, it should be confirmed in further engine research carried out in low temperature conditions. In this study the diesel smoke opacity (SO) was also measured in the condition of a free acceleration test according to requirements of the United Nations Economic Commission for Europe (ECE) Regulation No. 24. Results of these tests demonstrate that the diesel smoke opacity is reduced even by 55% for DEE40 blend compared with RO.