AC system's lubrication amount?

The oil spec is PAG 150--68.00 ounces. General Motors issues Bulletin # 02-01-39-004B replacing PAG 150 oil with a lower viscocity oil. Thus, now indicates PAG 46 (P46D) oil for those vehicles.
There is a high pressure side and low pressure side to the system. The high vapor=compressor to the condensor. Low side vapor=compressor to evaporator. Your system will use R134a freon.

The A/C is a sealed system and when the compressor fails it circulates debris throughout the A/C system and contaminates it. Before replacing the compressor several other A/C parts have to be checked or changed.
Typically, the condenser should be flushed to remove any debris or contaminated compressor oil. Use approved flushing agents (aresol or liquid pour types), that evaporate quickly and don't leave any residue in the system. You will also need access to 'DRY' compressed air or nitrogen to push the flush through the system. Nitrogen (an inert gas), is best because it doesn't introduce moisture into the system. You need to do this a couple of times.
Accumulator or receiver drier should be replaced when you are replacing your A/C compressor. If don't replace your accumulator or drier you will probably void your compressor warranty. It's virtually mandintory to replace the orifice tube or expansion valve. The openings are usually about .050" and are quickly plugged. Be sure to clean all hose assemblies internally prior to installing your new compressor. Not doing this could contaminate your new compressor. Flush both ways until the flush agent exiting is clean, you will need to remove the hose assemblies to do this.
After you have cleaned, inspected and replaced all the parts, you connect the vacuum pump and remove the air from the system. Make sure it holds pressure. Then recharge the system with the proper freon and oil to the system specified levels.

No matter why you are replacing the A/C compressor there is a lot of other related work that has to be completed before you install the new compressor. Hope this helps, good luck.

First if you do not have a vacume pump you cannot do this repair. Freon and oxygen make acid and will destroy you entire setup. Mount the compressor and take to a shop to have charged.