I'm replacing the a/c compressor in a friend's '99 coupe.
What is the correct GM recommended viscosity PAC oil for a 1999?

Advance Auto has light, medium, and heavy Pac oils for R134a systems.

 

This is what the service manual says:

Refrigerant Recovery and Recharging
Tools Required
J 39500-B Air Conditioning Refrigerant Recovery, Recycling and Recharging (ACR4) System


Caution
Avoid breathing the A/C Refrigerant 134a (R-134a) and the lubricant vapor or the mist. Exposure may irritate the eyes, nose, and throat. Work in a well ventilated area. In order to remove R-134a from the A/C system, use service equipment that is certified to meet the requirements of SAE J 2210 (R-134a recycling equipment). If an accidental system discharge occurs, ventilate the work area before continuing service. Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers.



Caution
For personal protection, goggles and gloves should be worn and a clean cloth wrapped around fittings, valves, and connections when doing work that includes opening the refrigerant system. If R-134a comes in contact with any part of the body severe frostbite and personal injury can result. The exposed area should be flushed immediately with cold water and prompt medical help should be obtained.



Notice
R-134a is the only approved refrigerant for use in this vehicle. The use of any other refrigerant may result in poor system performance or component failure.



Notice
To avoid system damage use only R-134a dedicated tools when servicing the A/C system.



Notice
Use only Polyalkylene Glycol Synthetic Refrigerant Oil (PAG) for internal circulation through the R-134a A/C system and only 525 viscosity mineral oil on fitting threads and O-rings. If lubricants other than those specified are used, compressor failure and/or fitting seizure may result.



Notice
R-12 refrigerant and R-134a refrigerant must never be mixed, even in the smallest of amounts, as they are incompatible with each other. If the refrigerants are mixed, compressor failure is likely to occur. Refer to the manufacturer instructions included with the service equipment before servicing.


The J 39500-B removes the Refrigerant-134a from the vehicle's A/C system. The recovery procedure uses one filtering cycle. The evacuation procedure uses an automatic multiple pass filtering cycle. These filtering cycles ensure a constant supply of clean and dry refrigerant for the A/C system charging.

The ACR4 recovery tank may have excessive refrigerant tank pressure. Excessive refrigerant tank pressure may be an indicator that the refrigerant tank contains excessive non-condensable gas (NCG). This contaminant is usually air. Air is most likely introduced into an A/C system by an incomplete refrigerant evacuation procedure. However, in some instances the charging station may be at fault. Follow the maintenance procedures as described by the equipment manufacturer to prevent excessive refrigerant tank pressure.

Refer to the J 39500-B ACR4 manual for operation and setup instructions.

Refrigerant System Oil Charge Replenishing
If oil was removed from the A/C system during the recovery process or due to component replacement, the oil must be replenished. For the proper quantities of oil to add to the refrigerant system, refer to Refrigerant Oil Distribution Specifications

 

All three different viscosity PAG oils at Advance stated: "not for use on GM HT6 compressors". My '01 shop manual doesn't specify the correct type of PAG oil either.

It looks like I'll need to make a trip to a Chevy dealer on Monday.

 

GM p/n 12345923 is the recommended a/c compressor oil.

It is a PAG oil with a viscosity of 150.

 

Does the C5 system use Oil in the compressor or oil in the lines? Some R134 comes with oil in it. I thought I read somewhere that the new GM system don't require oil in the lines to lube the compressor as the compressor has a stand alone oiling system.