how to add oil to ac compressor

By Tsukasa Azuma

Last updated Jan 20, 2021

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The air conditioning system in an automobile needs a specific amount of oil to work, just like the engine. You should have a clear idea about how much PAG oil to add to AC system to save it from unpredicted failure.

Which AC Components Require an Oil Refill?

The compressor is the AC unit component that needs adequate oil to run smoothly. Normally, there is no need to add oil to your vehicle's existing AC system, unless you have changed the compressor or there is a leak, letting oil dripping from the system.

A compressor needs a sufficient amount of oil for lubrication. It has some cylinders to compress refrigerant gases, which creates heat and friction. Oil in the system controls that heat and reduces friction by making the parts more slippery.

If there is a leak in the system, fix it first before adding oil into it. Otherwise, the system will require more oil soon and may lead to the failure of some parts.

What Is PAG Oil?

PAG oil, or Polyalkylene Glycol, is specially created for the AC compressors of automobiles. The fully synthetic hygroscopic oil is a compressor lubricator for the AC units that use R-134a refrigerant.

Besides knowing how much PAG oil to add to AC system , you also have to use the correct viscosity oil. Each PAG oil type has a number such as PAG150 or PAG VC-46. This number refers to the PAG viscosity, similar to a number like 10W30 indicates the viscosity of a regular engine oil.

You have to look into the owner's manual to find out the correct PAG oil viscosity for the AC's compressor.

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H ow M uch PAG O il to A dd to AC S ystem

The compressor of the AC system is likely to have specifications regarding the amount of oil to be added. You must check the owner's manual before adding more oil.

The AC system in most modern vehicles needs a total of 4 ounces (120 ml) of oil. So, checking the manual is a good idea to be sure of the exact amount and to avoid over- or under-filling the system. A low level of oil may cause compression failure, and overfilling will also hurt cooling performance.

how much PAG oil to add to AC system — Don't overfill the system. (Photo Source: acforcars)

Here is the amount of PAG oil that different AC components require for their smooth operation:

Compressor = 1.4 ounces
Evaporator = 1.5 ounces
Condenser = 1 ounces
Accumulator = 1 ounces
Hoses = 1 ounces

Flushing the entire system is recommended before adding oil or refrigerant. When you are replacing a part, such as a compressor or an accumulator, you should always add the oil that has been lost during the replacement.

However, the total amount of added oil should never exceed the system's oil capacity. So, when calculating how much PAG oil to add to AC system , always remember to keep the total amount under 4 ounces or whatever the capacity of your car's AC system is.