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A/C question: how much oil to add on a recharge?

For a full system evacuate and recharge (R134a, '94 Jag XJ6), how much oil should go into the system with the refrigerant?

According to my Haynes techbook, you need 4 to 5 oz.

Base your oil recharge on how much oil came out during evacuation. You can put to much oil in the system. AC work goes to the shop IMHO

I agree. I do not classify automotive AC work as do-it-yourself.

An evacuation only removes air and moisture. It doesn’t remove oil. In order to remove oil from an AC system, the system would have to be disassembled and the components flushed with a special solvent. So if you didn’t do this, there’s still the old oil in system components. And adding any more will be too much.



or drain the compressor,and see what is left,subtract that from the manual,and there you have the evap,condenser,receiver dryer.

just assume there is 3/4 left and add the difference.

best bet take it to an A/C shop.too many variables for me to explain.

Have you ever used a recovery machine? Maybe I didnt make my self clear. When you recover the refridgerant charge oil comes out with it the charge and the oil are mixed together.The oil and the refridgerant are seperated inside the recovery machine,after every recovery you drain away the oil and measure it this is how much you replace. Now if your recovery technique was to vent to the atmosphere you dont know howmuch oil to replace. The oil loss occours when the charge comes out.I answered the question as if the charge was properly recovered.You are correct if you are at the point of evacuation you have already dealt with the recovery of the charge/oil mixture.I did conclude that on a 94 we were dealing with a system that had its charge properly recovered.I should have stated base the amount of oil you put back in on how much comes out upon charge recovery.And as pointed out you can drain all old components and add accordinally.But pay attention how much oil comes out upon charge recovery

Yes. I’ve got my own refrigerant recovery machine. And I know exactly how they work. And you are right. When refrigerant is reclaimed some oil is removed with the refrigerant.

Now I want you to look at the original post. Do you see anywhere where it was mentioned that a reclaiming of refrigerant was performed on the system? I don’t. It sounds to me like they just hooked up a vacuum pump and evacuated the system of air and moisture. And when you do this no oil is removed. Besides, if the poster was using a refrigerant recovery machine, wouldn’t you think they would know that what was collected in the recovery machine is the amount to be replaced? Instead asking this question here?

Get a grip!


If you want to evacuate systen must be empty. I did conclude that proper recovery was preformed.It didnt occour to me that someone who new about evacuation would also vent to the atmosphere. I gave the guy to much credit. I made a mistake in making a conclusion.So the guys got a pump no recovery machine and no clue.In my post I did acknowledge you were right about no oil being removed during evacuation.

If you buy refrigerant that already has oil in it, you won’t need to worry about it.