R-134A Oil Type For 1996 A/C?

[Greg Gore]

Hi Folks:

I am finishing up a rather extensive job on a 96 and I just discovered the A/C is low. I would like to hook up the gauges and top it off with R-134A but would like to use an oil charge if available. It looks like there are several different types of oil used in R-134A systems such as POG, POE and a few different oil viscosities to pick from. What would be the recommended oil type for my 96 and is it available in an oil charge. I am hoping I wont have to evacuate in order to add oil before adding refrigerant. I am told if a system is low on refrigerant it will need oil added as well as R-134A. Thanks in advance!

Greg

[ToolGuy]

You need PAG Oil. And you can add it at any time. One way is through a syringe into the low side hose. You will need to know how much to add or was taken out if recovered. Sounds like you did not recover because you were not aware so hopefully someone here can tell you what to add if low or where to start to add.

[Greg Gore]

Apparently there are several types of PAG oil available and I think PAG 150 high viscosity oil was originally specified for the 96 Corvette. The GM part number for that is 12345923 but has been superseded by 12378526 which is PAG 46 I think. Can anybody shed some light on this? I still have my original compressor and would like to be sure I won't hurt it.

Thanks, Greg

[Greg Gore]

The compressor is a Denso 10PA. Looking up 10PA specs on several Internet sites reports the recommended oil is PAG 46. The label under the hood states to use only GM part #12345923 and several sources report this is PAG 150. I am told part #12345923 has been discontinued and is superseded by #12378526 which is PAG 46.The plot thickens! Help!!

[irfgt]

Unless you have a large visible oil loss then I would not add any oil. If you had that big of an oil loss, then a repair would be in order. Just top off the freon and watch the pressures closely as you do.

[bradfordsvettes]

to much oil in the system is as bad as low oil level it could bind up the compressor if way to much or you lose the ability to have a full freon charge imho 1 oz would be the max if you feel the need steve

[Greg Gore]

Thanks for the info. Main reason I asked is the car has 110K miles; it's a nice car and otherwise all original but I don't know the history of previous AC service if any. The AC is currently not as cold as it should be and I wondered if an ounce or two in an oil charge would be called for instead of just topping off with R-134A only. A previous car (not a GM car) needed an R-134A recharge every year until someone suggested an oil charge. It did not lose freon anymore after that. I realize this may not be the same thing but thought I would ask those of you who have a lot more knowledge and experience with it than I do.

[LLC5]

Just adding oil to the system will not stop a leak. Too much oil or R134A can damage components and diminish cooling. The only way to do it correctly is to evacuate and recharge the system. Adding 1/2 oz of oil shouldn't hurt anything if you have never had a leak or component replaced. Leaks or component replacement requires the correct of amount of oil to be installed, per component. If you do want to just add oil to the system, you can do it on the low side fitting, but it won't help your cooling.

[Greg Gore]

That's what I would have thought too but a friend who is a former longtime GM service department tech advised my to try some oil in the one I was having to recharge every year and for whatever reason it is still holding the topoff oil-charge I put in about four years ago. I guess the reason I asked is maybe the PAG oils behave a little differently than mineral oil the older R-12 systems used I don't know, but the thinking is if freon leaked out maybe some oil could have too. I don't see any evidence of prior work and I don't know how you could check the amount of oil without evacuating and doing a complete recharge along with the specified amount of oil. I can sure see where too much oil just displaces freon and would diminish cooling capacity. How can you know you are OK on oil level without guessing?

[LLC5]

Any time you lose freon, oil is lost also. How much is lost is a guess.

The only sure way to know how much oil is left in the system is to remove the compressor and drain the oil from it, and measure how much comes out. Add to that amount the oil in the rest of the components (evaporator, condenser, hoses, etc) and you will come up with a total. Subtract that from the system total amount of oil (should be in the shop manual), and you will know how much oil is needed, or if it is overfull. Each component holds a certain amount of oil and should be listed in the shop manual.