Tom Piper

From what I read, GM used high viscosity PAG oil in their R134a systems.
Some of the other OEM use a lower viscosity.

What are the pros and cons of each?

Is there a benefit to buying the PAG oil at a GM dealership over the after-market?

I know that PAG oil should not be used in a system that had mineral oil in it -- such as converting from R12 to R134a.

Tom Piper

Greg Gore

I am also looking into this one as I have uncovered a bit on a mystery concerning recommended refrigerant oil for my 96. The compressor is a Denso 10PA and according to a label on it the recommended oil is type ND8. An Internet search for ND8 oil info results in several sites reporting ND8 is type PAG 46 oil. An Internet search for Denso 10PA service info finds several sites reporting and recommending PAG 46 oil. Here is where the plot thickens. The label under the hood states to use GM part #12345923 refrigerant oil or equivalent and several Internet sources report this is PAG 150 oil. Apparently GM part #12345923 has been discontinued and is no longer available but is superseded by part #12378526 which is PAG 46 oil. A search of GM part #12345923 results show it was primarily recommended for GM vehicles using the Delphi compressor. Still trying to sort this one out before I buy oil for mine.

Tom Piper

Thanks for the reply.

Please keep me informed on an any other information on this.

Do you know what GM uses in the C5 A/C systems?


Tom Piper

Greg Gore

Some of the search results turned up info regarding oil recommendations being different for GM cars built after 2002 so it is possible the oil used in early C5 production was different than that for later C5. I also found a Power Point presentation related to a European engineering study comparing various properties of ND8, PAG and POE R-134A refrigerant oils. I was a little surprised at discovering the ND8 did not fare particularily well in its ability to lubricate bearings according to the durability portion of the test. I found a lot of info issuing caution against using PAG type oils from containers not tightly sealed as the PAG's are very hygroscopic. Additionally I found a lab test where the moisture content of various containers of new PAG oils were tested and found to already contain too much moisture. The test stated that containers of GM #12345923 tested contained over 800 PPM water where under thirty was the recommended limit. I found info stating the more common varieties of PAG are 46, 100 and 150. Apparently the POE is ester oil that is more commonly used in R-12 conversions because of its ability to be compatible with R-12 and R-134A and mineral oil used in conventional R-12 systems. I think this bears looking into a little more.

davidnclearlaketx

Ask over here:
http://www.autoacforum.com/categories.cfm?catid=2

Great auto AC forum with very helpful and knowledgeable folks.

They can answer very specific questions on auto ac.

SunCr

I don't know for sure - but I don't think it matters with a rebuild; ie, you're pretty much starting from scratch. You want to be consistent with whatever you use and the last later model I rebuilt (my '97 S10) I went with an ester off the shelf without giving it a second thought - the Compressor and Accumulator were being replaced and what little PAG remained wouldn't have a problem with the Ester (at least according to everything I've read - and there never was a problem with this rebuild). Now if you're adding oil because it's been leaking - I wouldn't go with a different weight or type. As to the C5 (and C6), GM junked the cycling orifice system and is using a variable stroke Delphi or Harrison and I'd guess they're using whatever they feel costs the less but gets them through the warranty - that's pretty much how it is with everything they build. Those compressors always run, which from a longevity standpoint, should mean longer seal life and less leaks. From what little I've seen, early failures have nothing to do with the gas or oil, but a program glitch - corrected in 2002? - generating a handful of complaints because the temp door isn't where it should be on hot days. Solution has been to replace the Panel.