Other A/C Compressor Oils on the Market
PAG oils might reign supreme in the hierarchy of today’s A/C compressor oils, but that doesn’t mean there aren’t some very important exceptions to be mindful of. Polyalphaolefin (PAO) oil can be used as a replacement for some PAG oils, and is sometimes preferred because it doesn’t absorb moisture from the air like other A/C compressor oils do.
For hybrid-electric vehicles that use electrically driven compressors, polyol ester (POE) oil is not just recommended, its use is mandatory in many cases.
Using PAG oil in hybrids can be hazardous to the vehicle, but it can also endanger the technician since there is an electrocution risk associated with using the wrong A/C compressor oil.
“I have heard horror stories where a technician put regular PAG oil into their hybrid vehicle, and they ended up having to have the A/C system replaced because Toyota, for instance, has a system where the check engine light will come on and the A/C system won’t run if the computer detects a certain amount of electrical connectivity within the case of the A/C compressor,” Schaeber said.
Universal Oil
A number of companies market A/C compressor oils labeled “universal” that purportedly can be used in any car (hybrids notwithstanding), and with both R-12 and R-134a refrigerants.
With all the variations between A/C compressor oils on the market, the one-size-fits-all utility of universal oils would seem to be a godsend for automotive technicians.
But according to experts, the only thing universal about universal oils is the risk they pose to the vehicles they are used in.
According to a DENZO report, “Analysis of DENSO A/C compressor warranty claims shows that in a quarter of all cases, garages did not use the correct PAG oil that is needed for DENSO compressors. The use of incorrect oils, such as universal oils or oil mixtures, inevitably leads to seizure and damage. This is because universal oils, often preferred by garages, are PAO oils or mineral oils with a different viscosity to that of synthetic PAG oils. PAO oils do not mix well with PAG oils and with refrigerant R-134a or R-1234yf, leading to poor lubrication and increased wear. Furthermore, the different viscosities cause a thinner oil film to form between the cylinder and piston, leading to seizure or the reduction in the life expectancy of the compressor.”
According to Schaeber, not following manufacturer recommendations is a recipe for disaster.
“It would be like if Ford recommended using 0W-20 motor oil, and you go on and stick 10W-30 or 10W-40 in it,” Schaeber said. “You wouldn’t do that. If the engine calls for 10W-40, that’s what you’re going to put in there, but when it comes to air conditioning, some people think, ‘Well, it is just A/C oil. I’ll dump whatever I have in,’ which shouldn’t be the case.”
