Compressor Oil Fill

oil fill


(illustration: Sanden International)

Richard Hawkins is a technical advisor at 1-800-Radiator. He recently told MACS about a question he received from one of the company’s franchise offices.

I cringe whenever I hear a technician say that he puts ALL the oil into a system using a recovery/recycle/recharge machine. When you use a machine to install oil, it’s putting the oil in through the high-side service port, and it takes a long time for the oil to make its way around to the compressor – where it needs to be. If the service port happens to be located on the discharge line right at the compressor, and if it’s an expansion valve system, the oil must travel through the discharge line, through the condenser, through the drier, through the liquid line, through the expansion valve, through the evaporator, and finally through the suction line before it ever gets to the compressor. That can take a while to happen, and when the oil does get there, it will take a while for the proper amount to accumulate in the compressor.

Even if the high-side port happens to be located on the liquid line near the expansion valve, the oil still has to travel through the expansion valve, evaporator and suction line to get to the compressor, and oil doesn’t travel very fast through an expansion valve that might have an opening of only 0.035 inch. This is the worst way to install oil in a system (not to mention that the oil may be the wrong viscosity, because the machine might have PAG 46 in it and the compressor might call for PAG 150).

R/R/R machines were really only designed to put a small amount of oil in a system, to replace some that might have been removed during service, not to put in a full charge. The vast majority of the oil should be put directly into the compressor. It’s the only part in the system that requires lubrication.


The Mobile Air Conditioning Society’s blog has been honored as the best business to business blog in the Automotive Aftermarket by the Automotive Communications Awards and the Car Care Council Women’s Board!

When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.

If you’re a service professional and not a MACS member yet, you should be, for more information.

You can E-mail us at . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here  to find out more about your car’s mobile A/C and engine cooling system.

The 34th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Power Up  will take place January 16-18 2014 at the Sheraton New Orleans.


About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues.
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One Response to Compressor Oil Fill

  1. Owen Dela Paz says:

    How to add refrigerant oil for reflenishment when you add a rear cooling unit (evaporator)? Can it be put directly to the evaporator or in the suction line before the compressor. I have limited access to the installed compressor

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