Compressor Oil Change

How to change compressor oil...continued. This is page two. On page one of compressor oil change, I talked about compressor oil types, what not to do, and about when to change your oil.

This is the page where we get into discussing the actual oil change process.

If, after you have read the information, you have any questions, you can ask them on this page.

compressor pump

I have posted a photo of my DIY compressor, focussing on the compressor head, and the components that you will want to identify on your air compressor when it comes time for an oil change.

Oil Fill Port

Item #1 in the photo is the oil fill port for my compressor. It makes sense that it will be located on your compressor at a higher level than the oil drain port.

Not every compressor is the same, yet all oil lubricated units will have an oil fill port of some sort, and that port will allow oil poured into your compressor to flow down to enter the oil sump located under the piston head assembly.

Do yourself a favor and keep a small funnel handy when you go to pour oil back in. Otherwise, you may cause yourself a bit of a mess by spilling the oil as you pour. This is the voice of experience!

Normally the cover for the oil fill port is vented. Your compressor consumes a little (or sometimes a lot) of oil as it runs, and if the port were not vented, eventually a vacuum would form in the sump which would limit the efficiency of the lubrication process.

How Much Oil

Item #2 in the photo and on my compressor is a sight-glass that allows me to peer into the oil reservoir to see how full (or empty) it is. On my compressor, and typically on others with a sight glass like this one, the recommendation is to keep the oil full to the center of the red dot.

sight glass

Your compressor too must have some method of determining how much oil you need to add to top up your compressor sump. If not a sight glass like the one in the photo above, then probably the cap of your oil fill port also contains a dipstick.

Overfilling the oil sump will lead to maintenance issues for your compressor.

You must keep the oil level topped up (the cheaper the oil-lubed compressor, the more oil it uses, it seems) and you must not overfill it.

The Oil Sump

Item #3 in the photo above points to the compressor casing, inside of which is the oil sump.

The bigger the compressor, the more oil it will need, of course. Mine only holds a few ounces, so I take real good care not to overfill, but at the same time, I check the oil level every time I go to turn the compressor on, as it doesn't take long for it to go through those few ounces of oil, either.

Get The Oil Out

Item #4 in the photo above is the drain plug. Removing this plug will allow the oil to flow out of the sump.

Some compressors (the more expensive types I think) actually have an extension on the drain port to allow easier collection of the oil.

I've used a flat cake tin that slides in under the drain port. Or, you can fashion a drain funnel from a sheet of tin foil (folded a few times to make it more rigid) to help the oil to run into a catch bin of some sort.

Draining the compressor oil can get really messy if you don't contain the flow of used oil, and it is a witch to clean up. Take a care.

Oil Changing Steps

These are the steps I take in changing my oil.
  1. Like a car engine, the oil in the compressor will run easier if it's warm. Leave the compressor sitting in the sun for a while before you start the job, or let it run and fill the air tank before you start.
  2. Open the fill port to allow air to flow more easily down into the sump.
  3. Position your drain catchment / funnel or whatever you're using to help contain the oil, and carefully open the drain plug. You want the oil warm, but it might be quite hot, so take care.
  4. My compressor has a handle on the front, so when the oil stops flowing out of the drain port, I lift the front of the compressor to help void the sump of any residual oil.
  5. Replace the drain plug, and wipe any oil residue from the surface so that you can see if you have a leak.
  6. Pour fresh compressor oil into the fill port to the specified level for your compressor.
  7. Replace the oil fill cap.

That's it. You're done.

The waste oil is considered hazardous waste. Be environmentally conscious, and dispose of it in a proper manner.