A/C refrigerant oil longevity

They say car refrigerant oil lasts forever. I find it hard to believe. Do you know of any scientific evidence (studies) that shows that refrigerant oil retains its viscosity, and lubricant qualities forever in a car A/C system setting?

Secondly, Is crude refrigerant oil as effective in car A/C systems as synthetic refrigerant oil?

There are three oils used in A/C systems. Mineral oil is used in R12 sytems. PAG (polyalkylene glychol) oil is used in R134a systems, and POE (polyoester) oil which can be used in both R12 and R134a A/C systems.

Any of these oils will allow an A/C system to operate trouble free. However, if moisture enters the A/C system it reacts with the refrigerant and oil and turns acidic. And it’s this reaction that breaks down the oil in an A/C system. So if the system is is clean and dry, the oil should last indefinately.


As long as the system remains sealed, the oils and the refrigerant will outlast the life of the car.

My answer is the same as before and I agree with Tester and Mr. Meehan. If the system is sealed the refrigerant oil will outlast the compressor. There are no contaminants (clutch particles or combustion process particles) or moisture problems being added to the oil like you would see in a transmission fluid or engine oil application.

Compressor problems are not caused by failure to change the refrigerant oil; they’re caused by lack of oil or other influences such as pressure problems (sticking expansion valve, clogged orifice tube, too MUCH oil, etc., and in some cases they’re just worn out from age and high mileage.


 Once again, if the system is not leaking and it is cooling properly then leave it alone...............


For what it’s worth the compressor oil (and the compressor itself) has never been changed on my 94 Lincoln nor will it ever be unless it has a catastrophic failure. It’s still quiet and puts out ice cold air on a 100 degree day so one would think after 15 years and almost 230k miles that if changing refrigerant oil was a necessity this one would have dropped long ago.