Following AC System Service, How Much Oil Is Needed?

So, you just got the parts in for an AC job. You’re replacing the compressor, and now you’re wondering how much oil should be added to the system?

This has confounded technicians for decades because it’s really unknown how much is already in the system and it’s not going to be on that label underneath the hood on most vehicles. The key is to look up the quantity of oil for the system and also what components you’re replacing. Depending on the manufacturer, you may have to add only two ounces of oil if you’re replacing an evaporator, three ounces for replacing the condenser. In some cases, you may have to use four ounces when you replace the compressor, but this is going to change depending on the vehicle.

In other words, as vehicles have changed, they require less refrigerant in the system and also less oil, so it’s critical to get the correct amount of oil for the system. This may require using your recycled recovery machine to pull the oil from the system and then maybe even take off the compressor to see what is remaining.

Also, if you’re ordering that new compressor, read the instructions that come in the box. Some compressors will be shipped with shipping oil. This oil is designed to prevent corrosion inside the unit while it’s coming to your shop. Some of them may have the correct oil in the system – as well as the correct amount – but make sure you’re checking it with a graduated cylinder to verify that that is the correct amount for the vehicle that you’re working on.

In terms of picking the correct oil, make sure you’re looking at the service information. Again, most of the vehicles you’re going to see out in the field, have PAG oil. It’s typically PAG 46, but there are some applications that have compressors that require a specific oil for the system.

Keep these things in mind after that refrigerant job, and you’ll make sure that you have the correct amount of oil in the compressor and the AC system.