HVAC Compressor Oil for Your Equipment-Choosing

Indeed, knowledge is power. HVAC compressor oil is an essential part of any air conditioning system. Having the correct information on choosing the right HVAC compressor oil helps one save a lot in monetary terms and on maintenance as well. The type of oil you want to use depends on its viscosity. The oil’s thickness level shows its ability to withstand the shear stress when the machine runs.

Choose the oil that brings a good cooling effect to the machine. The oil should have excellent dielectric strength so that it would not interfere with the normal functioning of the compressor. First-time air conditioner users find it hard to choose the right oil from the market flooded with many oil brands. Due to this reason, the users effortlessly sway into buying any oil that may turn out to be harmful to the air conditioning system.

It is essential to read the manual or consult the manufacturer on the right oil to get relief from the fear of spoiling the system with the wrong oil. It should not have a high moisture content, affecting the system’s performance. Your system needs quality oil to give you quality service, so serve it well with the right oil, and it will give excellent service back!

Compressor Oil Properties


Viscosity is the way of measuring the thickness of the oil, which informs us of its ability to resist shearing stress. One of the viscosity measurement units is Saybolt Seconds Universal (SSU). It is achieved by putting the oil sample on the standard equipment at a preset temperature with a standardized orifice and allowing it to flow. The time is taken for this to soak save. The bigger the viscosity number, the thicker the oil and the slower it flows.

The measurement unit for viscosity is poise. Almost all the oil measured is under one poise. Therefore, the smaller scale called 1/100 poise or centipoise is often used.

Generally, a larger compressor with more significant gaps and parts needs thicker oil for the productive functioning of your equipment.

Chemical Stability

While using the compressor oil, always stick to the compressor manufacturers’ suggested oil as some oil may interact with the refrigerant in the machine. If the chemical reaction happens, sludge, carbon, and acids may be boomed, affecting your compressor’s efficiency and lifetime Strength & Moisture.

Compressor OilAs the compressor oil used in a hermetic compressor is often exposed to the motor’s coil, it must have outstanding dielectric strength. The bigger the dielectric strength, the more suitable the electrical insulating value of the oil.

Nearly all oils will dissolve a lot of moisture and water, which makes them undesirable. When water is in the refrigerant, ice will form if the temperature goes below zero degrees, causing issues for the expansion valve.

Copper plating may take place with the presence of refrigerant, oil, plus moisture in the system. Moisture within the oil also reduced the oil’s dielectric strength as water is a pretty good conductor. Hence, try cutting the moisture level in contact with the compressor oil as long as possible.

Typical HVAC Compressor Oil & Refrigerants

The two varieties of oils widely used in compressors are synthetic oils and minerals.

One type of mineral oil (MO) known as Naphthenic commonly uses the equipment.

Synthetic oils like esters, glycols, and alkylbenzenes (AB) have been used in refrigeration programs for a while with no problem.

CFC refrigerants like R115, R114, R113, R13, and R12 use alkylbenzene or mineral oil as their lubricants. Likewise, HCFC refrigerants like R409A, R401A, R22, and R123 usually use these lubricants in their design.

Recently HCFC and CFC refrigerant usage decreased because of their ozone-unfriendly properties. The use of new HFC refrigerants like R134a, R23, R32, R407A, R410A, and R407C has raised in HVAC equipment. These latest refrigerants use POE(Polyol esters) as a lubricant.

One drawback of Polyol esters is that it often absorbs moisture more than mineral-based oils. Hence correct ways should be used when handling this compressor oil to cut the contact of the oil with the environment. Metal containers are recommended in place of plastic containers to prevent moisture from entering the containers.


When repairing the compressor, always check with the compressor manufacturers to learn the type and amount of oil you can use for that specific refrigerant.

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