You can access the density following the example in this documentation: https://www.mathworks.com/help/physmod/hydro/ref/hydraulicfluid.html
For example, to access the density of Skydrol LD-4 at 50 degree Celcius:
>> props = sh_stockfluidproperties;
>> temp = 50;
>> [vis, den, bmod] = props.skydrol_ld_4.prop(temp);
where "temp" is the temperature (C), "vis" is the viscosity (m^2/s), "den" is the density (kg/m^3), and "bmod" is the bulk modulus (Pa).
