Understanding Compressor Oil Level

compressor oil level
(Last Updated On: August 3, 2020)

If your air compressor is oil lubricated, and there’s no guarantee that that is the case anymore, then you have to both maintain the oil level, and periodically change the oil.

I have received quite a number of emails from compressor owners wanting to change their compressor oil, and not knowing to what level they need to add the new oil after they have drained the old.

air compressor oil level

I don’t think that any oil lubricated compressor would be shipped to the store without some method of telling the owner what the oil level in their compressor is or has to be.

My compressor comes with an oil sight gauge a photo of which is above, and the specs for my compressor call for the oil level to be maintained and re-filled to the mid-way point on the red dot.

Made it! 🙂

I did a bit of investigating today. I went to the a couple of the local stores that sell air compressors for home DIY and light industrial use and checked out the compressors on display for sale. Every one of the oil lubricated compressors either had a sight glass like the one above, or the oil fill cap was a dipstick so that you could see using that stick to what level you had filled the oil in the compressor oil  sump.

Some of the oil free (non-oil lubricated compressors) did not make it very clear that no oil was needed for that particular compressor. The tip off was, almost invariably, that the compressor head was completely shrouded and there was no access to get to it even if it did have oil and an an oil change was needed. So, to be sure, I opened the baggie with the paperwork and checked the specs. Sure enough, if you couldn’t get to the compressor head, odds were good that this model was oil free.

Wish you could bank on that, but you probably can’t. Ask the store dude if it’s oil lubed or oil free. That’s the only way to be sure.

And make no mistake. Overfilling, while not as immediately bad as running out of oil in the sump, will create maintenance issues for an oil lubricated compressor as well. You need to keep the oil at the proper level all the time for optimum compressor performance.

Hello, I am Bill, the Compressed-Air-Man. I have years of experience in industrial and residential compressed air applications, air compressors and general pneumatics. I created this site to help professionals, students, and DIYers understand and properly implement and maintain compress3ed air systems.


  1. Hi great stuff you are doing.
    Can you help? The plastic see through oil sight gauge on my Nutool MNAC50 has broken, any idea where I could get a replacement or alternative?


    Go to http://www.about-air-compressors.com, click the troubleshooting link, then click on the parts needed link, and post your request there. Someone out there knows where to find one for you.



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