From the TSB 9501:
Porsche 928 S MY 1983-1986
Refrigerant
Type
grams w/ or w/o auxiliary air
12
1050 w/o
12
1200 w/
134a
860 w/o
134a
1030 w/
ND Oil 8:
Type ml / cc
12
270 (+/-20)
134a
300 (+/-20)
----------------------------------------------------------------------
Porsche 928 S4-GT MY 1987-1989
Refrigerant
Type
grams w/ or w/o auxiliary air
12
1050 w/o
12
1200 w/
134a
860 w/o
134a
1030 w/
ND Oil 8:
Type ml / cc
12
270 (+/-20)
134a
300 (+/-20)
----------------------------------------------------------------------
Porsche 928 S4-GT MY 1990-1991
Refrigerant
Type
grams w/ or w/o auxiliary air
12
1050 w/o
12
1200 w/
134a
860 w/o
134a
1030 w/
ND Oil 8:
Type ml / cc
12
120 (+/-20)
134a
130 (+/-20)
----------------------------------------------------------------------
Porsche 928 S4-GT MY 1992-1995
*** the TSB does not state this. Compressor is different 10PA20, but this is what I know. See WSM Page 87-129 for a 1993.
Refrigerant
Type
grams w/ or w/o auxiliary air
134a
860 w/o
134a
1030 w/
ND Oil 8:
Type ml / cc
134a
160 (+/-20)
====
I checked my GTS: it holds 860 gr R134a and 130grams oil. So it says on the conversion shield. No rear AC.
Theo
===
Up to 1989:
The system requires 950 grams refrigerant (no aux/rear AC) and 1150 grams with rear AC. This is based on R12 refrigerant. When R134a is used, a 80% charge must be used.
Oil is 280 +/- 20 ml in the system. R134a must use synthetic oil (Ester)
====
Here's some of my reference notes on
oil capacity:
- Porsche Technical Specifications, 90-91 S4/GT, 92-93 GTS, says:
Page 74, air conditioning, refrigerant oil in compressor: 280 +- 20 cm3 Densoil
6
- Porsche Work Shop Manual, Volume 4, page 87-90 says:
Refrigerant oil in Compressor:
Type 6E171 280 +- 20 c.c. Densoil 6
Type 10PA20C 120 +- 20 c.c. Densoil 6
- Page 87-129 says:
As of MY ‘93, For R134a, Compressor type 10PA20C, Refrigerant oil in compressor:
160 +- 20 c.c. Densoil 8