Density of ionic liquid (IL) 1-butyl-3-methylimidazolium tris (pentafluoroethyl) trifluorophosphate (short name BMIM][FAP]) at high temperatures and high pressures were measured. The measurements have been made at pressures up to 140 MPa for 10 isotherms between (273 and 413) K using an Anton Paar DMA HPM vibration tube densimeter (VTD). The measuring system was calibrated using various standard fluids (double-distilled water, aqueous NaCI solutions, methanol, ethanol, toluene and acetone) with well-known density data (Internationally accepted NIST standard data). The combined expanded uncertainty of the density (rho), pressure (P), and temperature (T) measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be (0.01-0.08) % depending on temperature and pressure ranges, 0.1%, and 15 mK, respectively. We have critically assessed all of the reported density data at atmospheric pressure together with the present results for their internal consistence to carefully select primary data to fit reference correlation, rho(0)(T). This correlation rho(0)(T) together with the present high-pressure density measurements (rho, P, 7) were used to develop two -parametric (c and B) and theoretically based Tait- type equation of state. The theoretical interpretation and physical meaning of the Tait's parameters (c and B) and their temperature behavior was discussed.