How Much Oil Does My Air Compressor Need?

How Much Oil Does My Air Compressor Need
(Last Updated On: September 19, 2020)

How much oil does my air compressor need? It’s often a straightforward question, but sometimes it is difficult to provide a simple answer. This page is addressed at the DIY air compressor owner and the users of these, relatively low cost, home and small workshop air compressors.

Know that if you have an oil-lubricated compressor, you will need to add oil to the sump from time to time. The normal operation of the compressor pumps allows small amounts of lubricating oil to migrate from the sump, up the cylinder wall, and into the air compression chamber. From there the oil flows into the tank along with the compressed air.

Pumps with bad cylinder seals will allow even more oil to leave the compressor sump.

How Much Oil Does My Air Compressor Need? Not Too Much!

Overfilling the oil sump on a lubricated air compressor can create problems. In fact, it is better to underfill the sump just a bit than overfill it.

How Much Oil Does My Air Compressor Need to fill

The logical first step to finding out how much oil the air compressor needs is to check the manual that came with the air compressor if you still have it. If your air compressor is oil lubricated, the manual will indicate so, and tell you how much oil the sump needs to be full.

The manual will indicate the exact amount of oil your compressor needs. Once you add the recommended amount of oil, find the oil sight glass on the compressor and check to ensure that you can see the oil clearly. More on the oil sight glass below. If at this point you are wondering what type of oil to get for your compressor, the Powermate Px P018-0084SP 100% Full Synthetic Air Compressor Oil, is a cheap, affordable option available on Amazon.

Of more use in checking the compressor oil, since who can find their compressor manual years after we bought the darn thing, is to use either the sight glass or the oil dip stick.

Best Air Compressor Oils

Best Overall: Royal Purple 01513 Synfilm Recip 100 High Performance Synthetic Air Compressor Lubricant – 1 qt.

Best To Cool Down and Quiet Your Compressor: Mobil 101016 Automotive Accessories, 1. gallons

Best To Extend The Life Of Your Compressor: Ingersoll-Rand Ingersoll Rand 32305880 Start-up Kit for Model 2420/2340/2475 Air Compressors


Compressor Oil Level Sight Glass

Once you add oil to your compressor, the next best thing to do is to check the oil level sight glass. The oil sight glass helps to determine the level of oil in the air compressor. Normally, this glass may be found on the sump tank in a rotary screw compressor or on the base of the pump for a reciprocating type compressor.

Compressor Oil Level Sight Glass

Look on the side of, and near the base of the pump, which is where the oil sump is located. You may see a sight glass similar to the one in the photo above.

If your air compressor uses a sight glass to help determine the oil level in the sump, examine yours, and see where the oil level is. If the oil level is at the middle of the center dot (it’s a red one on this sight glass) then your oil is at the correct level. An oil level any higher than this would be considered over-filling.

So, ideally, you want the oil level to be in the center of the dot. If you find that the oil level is below the dot, then add more oil. If the oil level is above the dot, you added too much oil.

No sight glass? Then if your air compressor is oil lubricated, it will almost invariably have a dipstick.


Compressor Oil Dipstick

The oil level dipstick is typically part of the oil-fill tube cap.

Compressor Oil Dipstick

The oil fill cap inserts into the oil fill tube, typically found near the tip of the oil sump, as can be seen in the following image.

Compressor oil system on compressor - www.understanding-air-compressors.comWhen the oil fill cap, and dipstick, are removed from the fill tube, it will look something like this next image.

The correct oil fill level should be indicated on the leg of the dipstick.

The dipstick and the cap have a small hole in them to allow the oil sump to breathe. Absence of the hole, or if the hole is plugged, may lead to pressure or vacuum to develop in the sump. If you don’t already have a compressor oil dipstick, you can get this Rolair Oil Dipstick on Amazon.

Other Compressor Oil Dipsticks On Amazon

Hitachi 881469 Replacement Part for Power Tool Oil Dipstick

DeWalt D55151/D55152 Compressor Replacement (2 Pack) Dipstick 5140016-78-2PK


No Dipstick & No Sight Glass

What if I want to check my air compressor oil level but the compressor doesn’t have a sight glass and aI don’t have a dipstick. If this is the case with your air compressor, you may want to double check to be sure that it actually is a compressor to which you must add lubricating oil. Many modern compressors are built to be self-lubricating, and no external lubrication is needed.

In the event your compressor is – for sure – oil lubed, does not have a sight glass, does not have a dipstick, you have a couple of options.

Take the measurements of your oil sump. Close counts. Take a photo of it from two sides. Take the photo and the dimensions with you to the compressor store. Find a compressor on display with a comparably sized oil sump, find the manual for the new compressor, and note the correct oil level for that compressor, and use that as a guide for yours.

Or, with a handy supply of rags (you will need them) and a large container, pull the sump drain plug (can be seen in the image above) and drain all the oil into the container. Measure the volume. Use an ounce or two more than this volume to refill the oil sump with fresh oil. Cross your fingers!


What If I Added Too Much Oil?

So while there is a risk in adding too little oil and causing friction and overhearing, there is also a risk in adding too much oil to your air compressor. Unlike adding oil to cars, where we normally fill up to the top, doing that is not a good idea for air compressors. One of the main indications that you added too much oil id when customers say:

“My compressor is spitting oil”


“There is oil coming out of my compressor lines”

Both of these issues indicate that the air compressor was overfilled with oil and are just mechanisms to get rid of the excess lubrication.

Filling up your air compressor sump to the top can actually result in serious and significant internal damage to your compressor unit. Why is that?

compressor is spitting oi

Well, whenever you fill up the sump with excess amounts of oil, the oil will be come aerosolized, which means it will be converted into a fine spray when the compressor discharges.

This can damage the compressor as well as any related pneumatic tool, accessories and other peripherals attached to the compressor.

Moreover, oil in the compressor discharge can get into the airway and ruin the compressed air coming from the compressor.

Think about it, what if you are pumping your compressed air to atomize white paint but the oil gets into the compressor airstream and into the paint. What a mess! Many projects have had to be scrapped in the past because of issues like this. Another good example is oil getting into the airstream while sanding fine wood.


Why Do Air Compressors Need Oil?

Air compressors are made of many moving parts and require constant lubrication to prevent friction on the pistons or screws as well as all other moving parts.

This is why oil is very important of air compressors because, without it, there will be too much friction which may very well damage certain parts of the compressor.

Proper oil levels is important to keep your air compressor working efficiently and so you should make it a priority to check your oil levels regularly and know how much oil your compressor needs.


Before Adding Oil To Your Air Compressor

As we mentioned before, you should check your air compressor manual for the proper guidelines on adding oil to the compressor unit since different compressor brands and models will require varying amounts of oil.

Remember, to keep your compressor operating at its optimal, you will always need to make sure that it is operating at the proper oil level. This is why preventative maintenance is important.

If your air compressor is low on oil, you can grab the Powermate Px off Amazon, it’s a great, affordable choice.

Good luck!

Air Compressor Oil Change–Extend the Life of your Air Compressor


When Do You Change Your Air Compressor Oil?

Like with many things, the answer is, it depends. Some people only think of changing their compressor oil if the compressor oil becomes black. That’s not a good idea.

If your air compressor is running in a plant environment, one, or two or three shifts a day, you are probably changing the air compressor oil regularly, at about 200 hour intervals of use, or whatever that specific air compressor manual tells you.

But what of those of us at home with workshop air compressors that will not likely see 200 hours of compressor use over a number of years? You are, of course, keeping the oil in the sump to the correct fill level with new oil, as the compressor consumes oil. That is adding fresh oil, depending on how much your air compressor oil gets consumed. Even with that, you do want to change out the oil with a fresh supply once a year as a maximum interval between compressor oil changes.


Oil Is In My Air Compressor Air Line

Norgren, a major manufacturer of compressed air treatment products, reminds us that “coalescing filters do not remove oil that is in the vapor state in the supply air. Vapors are typically removed using an activated carbon filter. Always protect a vapor removal element by removing oil aerosols with a coalescing filter before the vapor removal filter.”

Sounds like good advice to protect the life of the activated carbon filter.

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.


    • I looked on line and think I saw an image of what the Able Cooke 340 Magnum air compressor looks like… I think! If what I saw was the correct one, then it’s a pretty small sump. I’d put the dipstick beside the hole for it and see how far it extends down into the sump. Or, I’d be OK with putting oil in until I could see it by about 1/2″ on the dipstick. Best I can do, not seeing a photo of the compressor, and no sign of any manual that I could find. Anyone else?

  1. I have a NuTool NuAir compressor 1997 built
    Model NA700
    Sadly I am struggling to find any information on how you put oil in it as there is no dipstick or viewing window as far as I can see .

    • John, I, too, haven’t found any information on your model NA700. However, I do know that NuAir is now FINI compressors, and you can perhaps get info at:

      Perhaps you might add a comment here with a photo of both sides of your compressor, preferably with the shroud off if there is one and we’ll have a look to see if we can assist?

    • Alvin, this is from the Ryobi manual which you too can download here:

      1. Place a suitable container underneath the drain to
      collect used oil.
      2. Remove the drain plug using a wrench.
      3. When the used oil has drained, reinstall the drain plug
      and tighten with the wrench.
      4. Unscrew the cap of oil fill hole.
      5. To refill, use a funnel to pour oil

      Hope this helps.

  2. I have an old late 70s era sears twin cylinder air compressor similar to a Speedaire 3Z406. I have no book for the unit. It’s been years since the oil was changed in this unit, so I thought it might be a good idea to put new oil in the crank case but don’t know how much to use, or what weight oil is appropriate. I did try to fill the crank case with a 16 oz container of compressor oil that I purchased at the local hardware store. It filled the unit up to the bottom threads of the fill plug, which seemed to be good enough. However when I ran the unit, after about three minutes of run time, the unit started to make screeching noises and before I could stop it, the unit almost froze up before I could pull the plug. That’s when I decided to let well enough alone and seek some advice. The compressor still turns freely, but I won’t run it again until I know I have the right amount of oil in the crank case. I can’t seem to find any answers on the web. Can you please advise me. I sure hope I didn’t ruin anything. Thanks much for your time. God bless and best to you. I eagerly await your reply.

    • Gerald, I take it that when you dumped the old oil out, you no longer have access to the old to see how much came out? In the absence of an oil sight gauge, or a dipstick on the oil fill tube, then the rule of thumb that works for me is to fill the sump with enough oil so that it reaches the bottom of the sump oil fill plug threads, not the drain plug, unless they are one and the same. Which plug did you fill to the bottom of the threads to, the one on the pump front at the bottom or the one up and to the right of that one? The higher plug should be the one to use, I would think.

  3. I have an old Brunner air compressor and there is no sight glass and no dipstick. It was my grandads so the manual is long gone if it ever had one. I would like to know how much oil to put in it. Single piston unit. Can’t find model number anywhere. Im really not trying to booger it up because it is a quiet good working pump, but I can’t measure the volume coming out if the plug pulled. Is this the best advice you can offer

    • Bob, there are so many air compressors in use today, so many styles and sizes of oil sumps. all general guidance information pages can only be that… general. Having said that, if this were my compressor, I would be comfortable filling the sump to the bottom of the drain plug threads.

  4. I drained old oil and when i try to fill it to correct level it doesn’t seem to fill correctly. Acts like it has air in it so I opened drain plug up enough to where it started draining thinking I’d get any air out but still not doing right. What the hell am i doing wrong or what’s happening here?

    • Roger, not knowing the make or model of the compressor you have, I can only surmise that the fill tube is fairly small and the flow of oil into the tube is trapping air that is making a bit of a blockage until the bubble clears. If you can monitor the fill level with the sight glass, then add oil in less volume, perhaps a small funnel, to allow air to vent beside the incoming air stream? Close the drain plug of course, since as soon as you start pouring oil in it will drain right out again, not not really solve the issue of the air dam, if that’s what the issue is.


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