The addition of oxygenated renewable fuels, such as ethanol or ethyl tert-butyl ether (ETBE) to standard gasoline may be necessary to comply with some environmental directives but could also prevent compliance with some fuel regulations and could also seriously change engine performance. From this point of view, the Reid Vapour Pressure (RVP), the distillation curve, the oxygen content and the density belong to the group of the most relevant parameters. This study evaluates the influence of the simultaneous addition of ethanol and ETBE on some physical properties of engine gasoline. The main conclusion is that the simultaneous addition of ETBE and ethanol changes the RVP, the distillation curve and the density in a way that can affect engine operation and the mandatory EN 228 and ASTM D4814 standards. Some opposite properties of both oxygenates could help to increase the renewable energy content without preventing compliance with these regulations. (C) 2015 Elsevier Ltd. All rights reserved.