I am wanting to replace the AC compressor and receiver drier myself. So, I took my Honda Accord 2007 EX V6 to a local Firestone to have the refrigerant taken out. I inquired about the right amount of compressor oil to put in it. They informed me that I don't need to worry, that whatever is in the new compressor, the machine with detect it and put the right amount with the refrigerant.

Is that true?

  • Wrong. What you really want to do is to remove the old compressor, drain any oil from it and put the same amount of new oil into the new compressor after fully draining it, then rotate the clutch hub 10 times when it's installed. Anything else is asking for trouble. Tell them to not put any oil inside and have a voice recorder inside your pocket as you do, without letting them know, so that you can sue them if they do anything wrong with the oil (provided this course of action is legal where you live, of course). I guess you're letting them handle the refrigerant charge (highly recommended).
    – Al_
    Aug 28, 2019 at 8:46
  • The old receiver will have some oil inside too. Drain as much as you can from it, measure it and pour this quantity of oil into the new compressor too, in addition to the quantity that was drained from the old compressor
    – Al_
    Aug 28, 2019 at 8:50
  • If you're replacing the compressor and drier, you might as well do a proper flush, in which case you can assume you have no oil in your system. After closing up the system and pulling a vacuum on it to confirm air-tightness, you can just put in the appropriate amount of PAG oil into your compressor, or you can buy R134a with a predetermined amount of PAG oil included, and top up with oil from a bottle.
    – Huesmann
    Sep 4, 2019 at 18:22

1 Answer 1


Unless there is a new miracle machine, that answer is flat wrong. How does the machine "detect" the amount of oil charge shipped with the compressor? How does it know if the compressor is new, or original?? Horsefeathers!

Usually you are required to drain as much oil out of the old compressor as possible into a measuring cup or graduated cylinder, and then drain ALL the oil out of the new compressor (into something clean), and then replace (match) the exact SAME amount into the new compressor that was drained and measured from the old compressor.

This insures fairly close matching of the total system oil charge, as there are several places (evaporator, condenser, receiver-dryer) that can harbor oil. Since the new compressor usually comes with a full vehicle oil charge (the documentation will tell you), installing the new compressor without removing the appropriate amount will result in too much oil in the system. Depending on the capacity of the system and how much extra oil was added, this can result in anything from no difference, poor cooling performance, all the way to severe belt drive and/or compressor damage.

The machine would have to be clairvoyant, and would need to remove excess oil shipped with the new compressor - not add more with the refrigerant charge.

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