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Compressor Oil

abbouddi on Sat March 07, 2009 1:35 AM User is offline

Year: 2007
Make: Mazda
Model: 6
Engine Size: 2000
Refrigerant Type: R134a
Ambient Temp: 35
Pressure Low: 18
Pressure High: 230
Country of Origin: Saudi Arabia

When I recycled and charged my refrigerant R134a, I have doubt that a little quantity of oil was removed from the system (maybe about 20 ml) I installed the new refrigerant, but I am not relaxed because I think there is less oil in my system. The workshop manual asks to use ATMOS GU10 oil.
my questions:
1- I can not find this oil in our market, may I use the below one (synthetic refrigerant oil)?
2- May I add little oil to the system when it is charged? or should I have evacuated and add oil and then recharge?
3- What are the consequences of low oil in the system? is it short term or long term? and which component is affected?
4- On the other hand what is the consequences of extra oil in the system?
5- When recycling the refrigerant (for me 470 grams) should I add some oil (for example 50 ml given that as per the manual total quantity of oil in the system to be 120 ml)

Thanks

mk378 on Sat March 07, 2009 10:10 AM User is offline

Removing the refrigerant for recycling removes only a trace if any of the oil. You should not add oil unless replacing parts. Too much oil will reduce cooling performance and may cause compressor damage. Adding a little oil "just in case" is not a good practice.

If you do need oil in the future and can't get GU10, PAG 46 seems to be the generic substitute. PAG is the chemical structure and 46 is the viscosity. The bottle you have is probably ester (POE) or PAO, but who knows for sure. (Unlike the "snow baby" refrigerant cans, this label does at least promise you're buying a full liter of something). There are different types of "synthetic refrigeration oil" used with R-134a and the different chemical types of oil should not be mixed in a system. So try to find a bottle that is lableled "PAG" (Poly Alkene Glycol). PAG 46 is the most common type used by almost all auto manufacturers in their late-model R-134a cars so it should be possible to find some in the market.

abbouddi on Mon March 09, 2009 7:49 AM User is offline

Thank you for your reply, what about other mentioned questions?

HECAT on Tue March 10, 2009 6:11 AM User is offline

2- May I add little oil to the system when it is charged? or should I have evacuated and add oil and then recharge?
Oil can be added to components when system is open (before evacuation), or it can be added to a charged system with an injector.

3- What are the consequences of low oil in the system? is it short term or long term? and which component is affected?
A low volume of oil will not migrate within the charged systems as designed. This limits the proper amount of lubrication from reaching the compressor, which will cause compressor damage in both the short term and long term; and ultimately compressor failure.

4- On the other hand what is the consequences of extra oil in the system?
Too much oil causes two problems. The compressor is a gas (vapor) pump and excessive oil can liquid "slug" or "hydraulic" the compressor causing compressor damage or failure. Excessive oil can also coat the inside of the heat exchangers limiting the thermal transfer process(their ability to absorb or release heat).

5- When recycling the refrigerant (for me 470 grams) should I add some oil (for example 50 ml given that as per the manual total quantity of oil in the system to be 120 ml)
It is common during the refrigerant recovery and recharge process to add a little (guess) oil back for anticipated loss. This is risky and requires some educated estimating (how much?) and acceptance of the risks (what if I am wrong?). How much oil comes out in a recovery process is usually little to none, and will vary from car to car and with the different recovery equipment available. I don't think it would be wise to add back such a high percentage of the full amount as you have suggested above.


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