A/C compressor oil

[speedyb-cc]

Does anyone know how much oil a c-171 compressor needs? These are a rotary and were used on mid-late 80's mopars. The new one I got says to drain oil and replace with oem oil. Should I put back the same amount that came out? Whats wrong with the oil they come with? I'm using r-134.
Any help would be greatly appreciated.
Thanks and God Bless
Bruce