Presented here are the thermophysical characterization and thermodynamic modelling of RAVENOL Calibration Fluid 2.5 which is used for the calibration and preservation of diesel engine fuel injectors. Accurate knowledge of the standardized fluid properties is an important component for engineering modelling to deliver the correct dose of fuel into the combustion chamber of diesel engines while reducing the occurrence of cavitation phenomena. The liquid density and specific isobaric heat capacity measurements were carried out up to T=423K at ambient pressure. The speed of sound moving through the liquid was measured from T=(300 to 423) K from ambient pressure up to p=200MPa. This plays a crucial role in fuel injection timing. With the combination of these data with high pressure, it is possible to accurately calculate the liquid density, specific isobaric heat capacity, coefficient of isobaric thermal expansion and isothermal compressibility at elevated pressures. Thedata obtained at ambient pressure were used to confirm the accuracy of the high-pressure experimental data by comparing them with the predictions of the Fluctuation-Theory Equation-of-State. The calibration fluid hasbecome the second ISO 4113 fluid to be characterized in this fashion.