Category: A/C system oil

How to add oil to air conditioning compressor ?

How to add oil to air conditioning compressor ?



How to add oil to air conditioning compressor ?


Oil in the A/C system is essential, primarily to lubricate moving parts, i.e., the compressor. It also enables heat to travel and dissipate from the compressor. As with refrigerant, oil in the A/C system must keep its chemical stability.


Insufficient lubrication due to the wrong type of oil and viscosity is the second most frequent reason for A/C compressor damage and failure.


Distinct types of a/c oil like PAG,POE or mineral oils with a different viscosity do not mix, leading to poor lubrication, damaged seals and increased automotive air conditioning compressor wear


The use of the wrong type of oil could result in the hvac compressor’s piston rubbing against the cylinder surface. If the oil is too thick, it is unable to properly lubricate the tight space between the cylinder wall and the piston. Wrong oil viscosity can result in more internal friction, leading to an increase in compressor temperature and inevitably compressor damage.


Blending or mixing of diverse types of oils may result in a new different type and oil viscosity. This oil contamination build-up to the point where it can block the flow of refrigerant and oil, leading to poor lubrication and seizure of the compressor and major system failure.



Refrigerant moving oil and cooling down the A/C Compressor


it is extremely important that the engine not be run on a vehicle with a clutch less compressor if there is no refrigerant in the A/C system. This is because the compressor depends on refrigerant to carry lubricant inside of it.



How much oil should I add after a/c compressor replacement ?


After the refrigerant system has been charged and ran at the factory, the refrigerant oil in the A/C compressor is dispersed throughout the refrigerant system. The A/C receiver/drier, A/C evaporator, A/C condenser and the A/C compressor will each keep a significant amount of the needed refrigerant oil.

The refrigerant oil level in a new A/C compressor must first be adjusted prior to compressor installation.


Oil balancing the a/c system:

  1. Measure the oil recovered from the system by recovery/recycling/recharging station.
  2. Drain and measure the oil left in the old compressor using a beaker.
  3. Drain the new compressor and refill it with the same amount of oil removed from the system and old compressor .
  4. For Example :if 2 oz of oil are recovered from the system and 2 oz of oil was drained from the old a/c compressor, drain the new replacement a/c compressor and then add 4oz of the proper oil type and viscosity to the compressor before installation.



Installing the ac Compressor without balancing the oil in the system, gives a considerable risk of liquid lock, due to too much oil in the A/C system! When adding oil to the ac compressor in your car one out of two methods could be used and the right one will depend on the type of compressor. Oil could be added through the ac compressor oil service port or through the low side or intake of the compressor. Always add oil through the oil service port if it comes with one or compressor damage may result.


Most reclaim/recycling recharging stations will measure the lubricant being removed during recovery. This amount of lubricant should be added back into the system after the repairs are done.


How could the oil in my car’s A/C system be low?


Leaking automotive air conditioning systems will leak out refrigerant and the oil that resides inside of the compressor.

Refrigerant oil must be added when an A/C condenser, A/C receiver/drier or A/C evaporator is replaced

Refrigerant oil loss will be evident at the leak point by the presence of a wet, shiny surface around the leak.


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Drive system belt.A/C system oil balance

Which oil is used in A/C compressor?

Which oil is used in A/C compressor?

Automotive air conditioning systems use different type of oils and the specific type of oil will vary depending on the type of refrigerant, the type of ac temperature range system and ac compressor. Hybrid and electric vehicle compressors use different types of oil compared to conventional engine system compressors.


The refrigerant oil required by the auto ac system depends on a number of factors ,but it is primarily dictated by the type of refrigerant used in the system.R-12 car systems used a mineral oil. Mineral oil mixes well with R-12  without breaking down and losing its lubrication characteristics. Mineral oil however cannot be used  to lubricate ac systems with R-134a refrigerant.R-134 systems require a different synthetic oil, polyalkylene glycol (PAG).There are different blends of PAG and POE oil; always use the recommended by the vehicle manufacturer or the replacement part manufacturer.

The lubricant oil used in automotive air-conditioning systems is a non-foaming, sulfur free grade specially formulated for use in cars a/c systems. New refrigerants like R-1234yf might use PAG 46 and are backwards compatible for use with R-134a systems, but the R-134a old PAG 46 oils are not forward compatible with R-1234yf systems.

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Different types of oil

A/C compressor oil.

Modern compressors no longer have a dipstick to allow the A/C compressor oil to be checked

All modern compressors require the oil to be drained from the compressor and measured in a graduated container.

If the system had a leak, the measured amount of oil may be lower than specifications. Always refer to the guidelines given by the manufacturer before adding oil.

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Different types of oil

Air conditioning system oil type and balance

Analysis of Denso A/C Compressor warranty claims show that in a quarter of all cases
the use of incorrect oils, such as universal oils or oil mixtures, inevitably leads to seizure and damage. This is because universal oils, are PAO-oils or mineral oils with a different viscosity to that of synthetic PAG-oils. PAO-oils do not mix well with PAG-oils and with refrigerant R134a or R1234yf, leading to poor lubrication and increased wear.

Air conditioning oil properly recharged and balanced.

Installing the Compressor without balancing the oil in the system , gives a high risk of liquid lock, due to too much oil in the A/C system!

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Car A/C compressor oil balance procedure.

  • Recover the refrigerant from the ac system before opening the system.
  • Remove the old a/c compressor from the vehicle.
  • Drain the oil from the old ac compressor and measure the amount removed.
  • Drain the oil from the new ac compressor.
  • Add the same amount of oil drained from the old compressor with fresh, clean proper type of refrigerant oil into the new car air conditioning compressor.
  • Install the brand-new automotive a/c compressor properly oil balanced.
  • Vacuum the a/c system.
  • Replace Drier
  • Recharge a/c system with proper type of refrigerant and amount.

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Too much oil or too little oil in the car ac system.

Too much oil will restrict refrigerant flow through the ac condenser and too little oil will decrease lubrication to the compressor.

Oil overcharge or undercharge impact on the car ac system.

Too much oil in the car a/c system could result in extremely high head pressures which will cause poor air conditioning performance and premature wear and failure of the auto ac compressor. If there is a surplus of oil in the air conditioning system, too much oil circulates with the refrigerant ,causing the cooling capacity of the a/c system to be reduced and the hvac compressor head pressure to increase. Too little oil results in poor lubrication of the automotive ac compressor and an increase in the heat of compression which shorten the life of the vehicle’s compressor.

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Do new car A/C compressors come with oil?


Does the new car ac compressor contain oil?

Many auto ac compressor manufacturers list the oil amount on the label usually on the hvac compressor itself, but not all. Some may show it on the under hood sticker in the engine compartment. The best  and most reliable way to determine the exact amount of oil in the new car ac compressor is to drain the new ac compressor and measure the amount of oil if any,   inside.

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