What PAG Color Says About Your A/C System

New PAG oil looks clear and clean, but over time it will change as it picks up moisture. The combination of moisture and R134a produces corrosive hydrofluoric acid. As the acid eats away at copper and other metals on system components, the oil will begin to turn orange. By far, orange is the predominant color of oil we see in failed compressors (in the worst cases, the oil is black). These compressors didn’t fail; poor maintenance failed the compressors.

The 75R section of your Red Dot catalog of all-makes parts has a new page showing the different colors of oil and what they say about the condition of the system. It also talks about the more common internal failures on a compressor, as well as the signs of physical defects that you should look for.

Next time you need a good visual to explain the benefits of system maintenance and receiver-dryers, check out that color chart in the catalog. Oil color is a great indicator of the condition of an A/C system. A picture says a thousand words about the need to keep your system moisture-free.

How to Choose PAG Oil

Refrigerant oil has one job: to lubricate the compressor. While all compressor OEMs recommend PAG-type lubricant, not every manufacturer uses the same viscosity oil. In a survey of suppliers, we found that 14 out of 21 compressor manufacturers use PAG oil with an ISO viscosity of 46. TCCI, Zexel, and Delphi use oil with an ISO viscosity of 100. Sanden USA uses SP-15, which has an ISO viscosity of 68.

Because systems vary in wear, applied forces, and materials used, always use the OEM-recommended lubricant.