Did the refrigerator stop cooling, but diagnostics showed a compressor malfunction? Often in such cases, we are talking not only about mechanical failure, but also about the loss of lubricating properties of the fluid circulating inside a closed circuit. Oil in the refrigerator compressor performs a critical function: it reduces friction of moving parts, removes heat and ensures tightness of the gaps between the piston and the cylinder. Without high-quality lubrication, the unit quickly overheats and fails, requiring expensive repairs or complete replacement.
However, you cannot simply buy the first oil you come across and fill it. Modern refrigeration systems use different types of refrigerants, each of which requires a strictly defined chemical base of the lubricant. An incorrect selection may result in additive reaction, acid deposits, and capillary tube blockage. In this article, we will look at what types of oils exist, how to select them correctly for the brand of freon, and whether it is possible to replace it yourself.
It is important to understand that a compressor is a sealed unit where access is limited. Unlike a car engine, you cannot simply drain the waste through a plug. The maintenance process requires special equipment and a clear understanding of the physics of the processes. Technical characteristics liquids directly affect the service life of the entire refrigeration unit, so the choice must be approached with maximum responsibility.
Functions and requirements for lubricants
Basic The task of lubrication in a refrigerator is to create a stable oil film between the rubbing parts of the piston group. But there is a second, no less important function: the oil circulates through the system along with the refrigerant, so it must be chemically inert. Lubricating ability must be preserved at extremely low temperatures in the evaporator and high temperatures in the condenser. If the oil hardens or loses viscosity, the compressor will seize.
In addition, the liquid must have excellent dielectric properties. The compressor motor windings are in direct contact with the oil-freon mixture. Any decrease in insulation resistance may result in a short circuit. That is why technical petroleum jelly or conventional motor oils are strictly prohibited for use.
⚠️ Attention: Never use oils with unknown additives. In a closed refrigerator system, they can precipitate and clog the capillary tube, which will lead to complete inoperability of the unit.
Cleanliness requirements are also extremely high. There should be no moisture in the system, since water, when reacting with refrigerant and oil, forms aggressive acids that corrode the metal from the inside. Therefore, storage and filling of oil should be carried out in conditions that exclude contact with atmospheric air.
Mineral oil: a classic for old refrigerators
Traditionally, mineral oil was used in household refrigerators produced before the mid-90s. It is produced by deep purification and distillation of crude oil. The main advantage is high lubricity and excellent compatibility with traditional refrigerants, such as R12 and R134a.
The structure of mineral oil is paraffin, which makes it sensitive to low temperatures. With strong cooling it can thicken, but in older systems with R12 freon this was not a problem, since operating temperatures were higher. For retro restoration of old equipment or repair of Soviet refrigerators mineral base remains the only right choice.
However, this type has a significant drawback: poor solubility in modern environmentally friendly refrigerants. If you try to fill a system with mineral oil with R600a or R404a freon, the oil will not return to the compressor, but will settle in the heat exchangers, disrupting heat transfer.
- 🟢 Ideal for R12 and R134a refrigerants.
- 🟢 Affordable price and prevalence in market.
- 🔴 Not compatible with new environmentally friendly freons.
- 🔴 Can wax at very low temperatures.
Synthetic oils: polyesters and alkylbenzenes
With the transition of industry to ozone-friendly refrigerants, new lubricants were required. Mineral oils have been replaced by synthetic oils, among which the most common are polyester (POE) and alkylbenzene (AB). Polyester oils have a unique ability to mix with any type of freons, including R600a (isobutane) and R407c.
The main feature of synthetics is hygroscopicity. They absorb moisture from the air literally before our eyes. If you leave a jar of polyester oil open for 20 minutes, the moisture content in it will exceed the permissible limit tens of times. This requires special care when working: the system must be vacuumed more thoroughly and longer than when using mineral water.
Alkylbenzene oils occupy an intermediate position. They are less hygroscopic than polyesters and are often used as a transition or blend. However, their use is narrowing, giving way to more advanced esters.
Why can't you mix oils?
Mixing mineral and synthetic oil can lead to the formation of a jelly-like substance that will instantly damage the compressor.
When choosing For synthetics, it is important to pay attention to viscosity. For household refrigerators, oils with ISO viscosity from 15 to 32 are usually used. More viscous brands are intended for industrial equipment or air conditioners.
Oil compatibility with types of refrigerants
The key point during maintenance is the correct selection of the oil-freon pair. Chemical incompatibility leads to mixture separation, loss of lubricating properties and corrosion. Below is a table to help you navigate the choice.
| Refrigerant type | Recommended oil | Base type | Features |
|---|---|---|---|
| R12 (Freon-12) | Mineral Oil | Mineral | Classic pair, high stability |
| R134a | POE / Mineral | Synthetics / Mineral | More often POE, but also works with mineral water |
| R600a (Isobutane) | POE / Alkylbenzene | Synthetics | Requires full synthetics, explosive |
| R404a / R507 | POE | Polyester | Used in freezers and display cases |
As can be seen from the table, for modern systems For R600a, which is found in most new refrigerators, mineral oil is no longer suitable. Here synthetic baseis required to ensure the return of oil from the evaporator to the compressor. Ignoring this rule is the most common cause of repeated breakdowns after unprofessional repairs.
⚠️ Attention: When switching from one type of freon to another (for example, during environmental modernization), a complete flushing of the system with nitrogen and removal of old oil is required, since mixing bases is unacceptable.
It is also worth considering that compressor manufacturers (Danfoss, Embraco, Secop) often indicate the recommended type of oil on the unit nameplate. If it says Polyol Ester, you should not pour mineral water there under any circumstances.
The process of replacing and adding oil to the compressor
Changing oil in a hermetic compressor is a complex procedure and requires skills. Simply “unscrew and fill” will not work, since a vacuum is created inside, and the system must be absolutely dry. Typically, the oil is changed during a major overhaul or replacement of the compressor.
The process begins with removing the old refrigerant and dismantling the old unit. After installing a new compressor (or preparing the old one for operation), it is necessary to open the service pipes. The old oil is drained through the cut tubes, tilting the unit.
☑️ Tools for changing the oil
To fill in new oil, use a special dispenser or syringe with a long needle inserted through a suction tube. The amount of oil is strictly regulated: usually from 200 to 400 grams, depending on the model. Overfilling is just as dangerous as underfilling: excess oil will create a hydraulic shock and worsen heat transfer.
After filling, the system must be evacuated. This removes air and moisture vapor. Vacuuming time for household refrigerators is at least 15-20 minutes. Then fill with freon and seal the filling tube.
Common mistakes when servicing compressors
The most common mistake is using oil “by eye” or what was found in the garage. Transformer oil or waste from a car engine contains impurities that will kill the refrigerator within a few days of operation. Even drops of another liquid can ruin the entire system.
The second mistake is neglecting evacuation. Self-taught craftsmen often simply bleed off the air with freon, considering this to be sufficient. The remaining moisture reacts with the polyester oil, forming an acid that corrodes the motor windings.
The third mistake is mixing oils from different manufacturers. Even if the base is the same (for example, POE), additive packages between different brands may conflict. Always try to use oil of the same brand as the compressor, or its proven analogs.
- 🚫 Filling oil without weighing (by eye).
- 🚫 Keeping the system open for a long time (more than 15 minutes).
- 🚫 Using copper tubes without nitrogen purge when soldering.
FAQ: Answers to questions about oils for refrigerators
Is it possible to mix mineral and synthetic oil in the refrigerator?
Absolutely not. Mixing will cause an emulsion or sediment to form, which will impair circulation and lubrication. If the system had mineral oil, and you want to switch to synthetic freon, the system must be thoroughly flushed.
How often should you change the oil in the compressor?
In household refrigerators, the oil is designed for its entire service life (10-15 years) and does not require scheduled replacement. It is changed only during repairs, when the system has been opened, or when the compressor burns out (when the oil is smoked).
Where can I get oil for a refrigerator compressor?
Specialized oils (Emkarate, Mobil, Bitzer) are sold in refrigeration equipment stores. As a rule, they are not available in ordinary auto stores, since this is a specific industrial product.
What is the danger of moisture getting into polyester oil?
Polyester oil is hygroscopic. Moisture causes hydrolysis, resulting in the formation of organic acids. They corrode the insulation of the windings, varnish coatings and metal parts, leading to short circuits and corrosion.