The density of the ternary system (n-heptane + n-octane + ethanol) at temperatures from (293.15 to 373.15) K and at pressures from (0.1 to 40) MPa was experimentally determined at twelve compositions and the results are presented here. Measurements were performed using high pressure U-tube cell DMA HP coupled with DMA 5000 vibrating density meter. To fit the experimental density values the modified Tammann-Tait equation was applied. Excess molar volumes were also calculated at all pressures and temperatures in order to explain to what extent the investigated mixtures deviate from ideal behaviour. Moreover, the influence of pressure and temperature on density was studied by calculating isothermal compressibility and isobaric thermal expansion coefficient. It was found that non-ideal behaviour of the ternary mixture is strongly influenced by pressure and temperature conditions. (C) 2016 Elsevier Ltd.