My book is fairly vague about the amount of oil for the compressor. I think the entire system takes 12 oz. The compressor takes 6 oz, but 3 oz will accumulate in the evaporator, and another 1 oz will accumulate in the condensor, and another 2 oz will be retained by the accumulator. So, if you are replacing the compressor in a system that has not had any oil leakage, you should put 6 oz of 525 viscosity oil in the compressor. It won't hurt to put an extra oz in just to be safe.
THE IMPORTANT THING IS TO USE 525 VISCOSITY OIL!!
Otherwise the compressor life will be quite short. When folks perform an R12 to R134 conversion and have compressor failure right away, its usually because they used the oil that came with the conversion kit, which is only 150 viscosity oil. You have to purchase the correct oil for the compressor!! Ester oil is available in 525 viscosity, but is not included with the little kits they sell because most compressors will work with the 150 viscosity oil. Unfortunately, R4 compressors will fail with 150 viscosity oil! Hope this helps!
'82 300D/4.3L V6