Did you know that your vehicle’s air conditioner compressor needs oil? Cars and trucks with air conditioning need an oil that mixes with the refrigerant. This keeps all the moving parts of your AC nicely lubed and functioning. It’s important to understand the role compressor oil plays in your vehicle if you want to get under the hood and tune up the AC.
What Is AC Compressor Oil
AC compressor oil is usually a synthetic oil that gets mixed with your car’s refrigerant. The three main purposes of the oil are lubrication, sealing, and the removal of heat. Compressor oils have the following three properties:
- Viscosity: A measurement of oil thickness, the viscosity number indicates the oil’s ability to resist shearing stress. Different cars will require different viscosity numbers. You must use your make, model, and year to get the right number. Alternatively, you can always use a vin lookup to get the same information.
- Chemical Stability: As the oil gets mixed with the refrigerant, the chemical makeup is very important. Not all oils mix will mix with all refrigerants. An unexpected chemical reaction can result in the formation of sludge, acids, or carbon in the AC unit. This can potentially damage the compressor and affect its performance.
- Dielectric Strength and Moisture: Dielectric strength refers to the amount of electricity the oil can withstand before breaking down and losing its insulating qualities. The oil should have a very low moisture content. Any water in the oil, when mixed with the refrigerant, could form ice at low temperatures and cause further problems.
How To Choose The Right AC Compressor Oil
With all this information about different oils, how do you know which one to get when you go to your auto parts store? There are many factors to consider, but the first one to look at is the age of your car.
If you are driving a car that predates 1994 you will need ester oil. Older cars used to run with R-12 refrigerant and mineral oil. This refrigerant was shelved when its ozone-depleting properties were discovered. The newer refrigerant, R-134a, works with pag oil. However, pag oil cannot mix with any remaining mineral residue in the car’s AC system. Therefore, these older cars must use ester oil.
If your car is around 1994 and newer (remember that different makes and models will have different years), it was built to use R-134a refrigerant. This means you can put in pag oil just fine. You will need to research which viscosity is correct for your make, model, and year.
If you’re driving a brand new car, it could be using R-1234yf refrigerant. This is the newest refrigerant on the market and was introduced because it has low global warming potential. Once again, you’ll need a new oil.
This time, however, the oils are proprietary. Chrysler has its own, GM has its own, and so forth. Talk to your local mechanic about which one is right for your ride. You can also do a little research online or at your local auto parts store.