Does the compressor contain oil?

By Richard Hawkins, MACS Contributor

A question that comes up frequently on A/C tech lines is: Does the compressor contain oil and if so, how much?  

A generic answer to that is: It may or may not contain oil and if it does, the amounts can vary.  Let’s take an in-depth look at that and the different paths it can lead down and why.

First, there is no standard that exists in the industry when it comes to oil being shipped in compressors.  It is a matter of whatever a particular manufacturer might decide to do.

A/C parts suppliers may have multiple manufacturers they source compressors from, it is possible to have two compressors that fit the exact same application from the same supplier and one might be dry and the other might contain a full system charge of oil, or a partial charge.

Here are some different statements that might be supplied with compressors related to oil and some things to consider related to the statements.

1. “Compressor is shipped dry. It is the responsibility of the installer to ensure that the correct amount of oil is used.”  That one is my favorite. No need to take time draining the compressor, (although I’ll tip it up and check it just to be 100% sure).

2.  “Compressor is shipped with a full system charge of oil and no oil adjustment is necessary.” That is indeed possible, but there are several things to consider here that could result in a system having the wrong amount of oil in it if this statement is taken at face value.

A. It is possible that it could be the correct amount of oil needed if the system is dry (due to component replacement and flushing), but what if just the compressor is being replaced? That requires oil balancing as we have discussed in the previous blog articles and of course, a full system charge will be too much.

B. Even if a system is dry, it is possible that the “full system charge”   may be incorrect for the specific vehicle you are working on.  That is because compressors can fit a number of different applications and the system capacities can vary and supersessions and consolidations of part numbers can result in a unit ending up on a different vehicle than what the manufacturer originally intended.  

A prime example would be a compressor that is listed for a full-size van that could have come with either a single or dual A/C system.  An oil capacity of about 8 or 9 ounces is very common for these applications with a single system, but if it has a dual system, it might be more along the lines of 11 ounces or more (some even use 14 to 16 ounces) and a typical light truck compressor is not going to hold that much.

C.  Even if the labeling says the compressor contains a specific amount of oil and that is the total system capacity for the vehicle you are working on and the system is dry, you cannot be 100% sure you’re installing the correct amount of oil without draining the compressor and verifying it. A few years ago, I was installing a compressor on my Astro van which has a single system and an 8-ounce oil capacity, and the system was dry.  

The compressor label said it contained 8 ounces of oil, but when I drained it, only 2 ounces of oil came out.  It is not necessary to describe what would have happened if I had just installed that compressor without taking the extra steps to ensure the right amount of oil was going in the system.

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