Molecular　dynamics　(MD)　simulations　using　the　polymer　consistent　force　field　(PCFF)　were　adopted　to　investigate　the　pressure　and　thickness　dependent　density　of　squalane　film　in　a　nanogap　at　373　K,　with　three　different　initial　film　thicknesses,　and　for　a　wide　range　of　pressures.　The　equivalent　densities　predicted　by　MD　simulations　were　compared　with　the　empirical　data.　Results　show　that　the　squalane　atoms　tend　to　form　layers　parallel　to　the　confining　substrates　but　the　orientations　of　squalane　molecules　are　irregular　throughout　the　film.　In　addition,　distinct　excluded　volumes　are　not　found　at　the　interfaces　of　the　film　and　substrates.　Furthermore,　with　the　same　initial　film　thickness　h0,　the　film　thickness　h　and　compressibility　decrease　with　increasing　pressure,　but　the　compressibility　is　similar　for　films　with　different　initial　film　thicknesses.　The　equivalent　densities　predicted　by　MD　simulations　with　the　maximum　initial　film　thickness　(9.44　nm)　are　accurate　to　the　values　of　Tait　equation.　The　MD　simulation　with　adequate　initial　film　thickness　can　accurately　and　conveniently　predict　the　bulk　densities　of　lubricants.　©　2016,　Wuhan　University　of　Technology　and　Springer-Verlag　Berlin　Heidelberg.