Question: With so many oils available, which one should I use? Is there a good universal oil?
We know most shops don't like to stock all the different oils, and technicians often have a hard time determining which oil should be used in each system.
Here's some tips to get you going in the right direction.
First... Deciding which oils to keep in inventory isn't difficult, especially since most of the vehicles we work on are now R134a equipped. When R-134a replaced R-12, PAG became the factory specified oil.
You'll find three common viscosities when choosing PAG oil.
GM sometimes recommends oil which is close to ISO 135. In this case, PAG 150 is generally accepted by most technicians. We've had reports that ESTER oil used in GM compressors that specify ISO 135 may experience unusual knocking sounds. Most Ester oils have a viscosity closer to ISO 100.
Second... Keep an oil chart and specification guide close at hand. It's useful to have around when trying to figure out which oil goes where.
We are working on our refrigerant oil chart and should have that available as a reference here in time for A/C season.
For automotive A/C questions, please visit the Automotive Air Conditioning Information Forum at: https://forum.aircondition.com.